The United States has now had "direct contact" with Niger's junta leaders, but the conversations have yet to substantially move the needle as the West African nation -- a key ally on counterterrorism in the region -- faces an apparent coup, U.S. officials said.

U.S. Department of State spokesperson Matthew Miller acknowledged for the first time during a press briefing on Monday that American diplomats have been speaking with Nigerien military figures behind the attempted takeover but said they "remain in touch with" the country's democratically elected president and other leaders in West Africa.

"There has been direct contact with military leaders urging them to step aside," Miller told reporters, insisting there was still a chance to turn things around despite the difficult realities.

"The window of opportunity is definitely still open," he added. "I don't want to put an assessment on when that window would be closed other than to say that using diplomacy to achieve this objective is our top priority with respect to Niger and we continue to pursue it."

Acting Deputy U.S. Secretary of State Victoria Nuland was among the American diplomats who recently traveled to Niger to meet with the power-players in the insurgent government there, telling reporters later Monday that the goal was "to get some negotiations going and also to make absolutely clear what is at stake in our relationship and the economic and other kinds of support that we will legally have to cut off if democracy is not restored."

But they were unable to make any significant progress despite speaking for more than two hours with Niger's self-proclaimed top defense official, according to Nuland.

"The conversations were extremely frank and at times quite difficult," Nuland said. "It was not easy to get traction there. They were quite firm in how they want to proceed."

Nuland told reporters that her requests to see Nigerien President Mohamed Bazoum went unfulfilled and she was also not given an opportunity to meet with Gen. Abdourahmane Tchiani, the commander of Niger's presidential guard who has been declared the new head of state.

“I hope they will keep the door open to diplomacy," she added. "We made that proposal. We'll see."

Despite the setbacks, Nuland said the U.S. was not yet ready to officially declare that a coup had indeed taken place in Niger.

"Obviously, we are at the stage where assistance is paused. There is still a lot of motion here," she told reporters. “It is not our desire to go there, but they may push us to that point."

On July 26, a group of mutinous soldiers led by Tchiani placed Bazoum and his family under house arrest in the Nigerien capital of Niamey. They then announced on Nigerien state television that they have "put an end to the regime" of Bazoum due to "the continuing degradation of the security situation, the bad economic and social governance." The group, which calls itself the National Council for the Safeguarding of the Country, said "all institutions" have been suspended, aerial and land borders have been closed and a curfew has been imposed until the situation is stabilized.

"The defense and security forces are managing the situation. All external partners are asked not to interfere," Tchiani, flanked by soldiers, said in the televised statement.

Bazoum's apparent ousting marks the seventh attempted coup in West and Central Africa since 2020 and throws into question the future of Niger, a landlocked country that has had four coups since gaining independence from France in 1960. Bazoum was elected to office in 2021 in Niger’s first peaceful democratic transfer of power.

As military leaders seized control last month, the streets of Niger's capital erupted in chaos as hundreds of people marched in support of the president while chanting "No coup d'etat." Thousands of others came out in support of the junta, waving Russian flags and holding signs that read "Down with France." Protesters also burned down a door and smashed windows at the French embassy in Niamey before being dispersed by Nigerien soldiers.

France, along with several other countries, has since evacuated its citizens from Niger while the U.S. partially evacuated its embassy in Niamey. Although the U.S. embassy remains open for limited, emergency services to its citizens there, routine consular services were suspended and Americans were being advised not to travel to Niger.

"We can confirm that our non-emergency U.S. government personnel and eligible family members have departed from Niger," a U.S. Department of State spokesperson told ABC News in a statement on Monday. "We were able to accommodate nearly 100 private U.S. citizens with the extra capacity on the charter flight that relocated embassy employees and their family members on August 4. Some U.S. citizens also departed on flights organized by our French, Italian, and Spanish organized flight partners."

The ordered temporary departure of non-emergency U.S. government personnel and eligible family members from the American embassy in Niamey has no impact on U.S. forces in Niger, according to U.S. Department of Defense spokesperson Brig. Gen. Pat Ryder.

The Economic Community of West African States (ECOWAS), a regional body comprised of 15 West African countries, announced sanctions against Niger on July 30 and threatened to use force if the coup leaders don't reinstate Bazoum within one week. The African Union and the United Nations have also issued statements condemning the apparent coup.

Guinea, a nearby nation that has been under military rule since 2021, issued a statement on July 30 expressing support for Niger's junta and urging ECOWAS to "come to its senses." On July 31, the military-ruled governments of Burkina Faso and Mali, which share borders with Niger, released a joint statement denouncing the ECOWAS sanctions as "illegal, illegitimate and inhumane," refusing to apply them, and also warned that "any military intervention against Niger will be considered as a declaration of war against Burkina Faso and Mali."

Meanwhile, Benin, Ivory Coast, Nigeria and Senegal -- all ECOWAS member states -- have indicated their willingness to send troops into Niger if the bloc decided to do so.

Senior officials within the U.S. Department of State told ABC News last week that ECOWAS is creating plans for military action if it becomes necessary but sees it as a very last resort.

In a televised statement on Sunday night, hours before the deadline set by ECOWAS, a spokesperson for the Nigerien coup leaders announced that the nation's airspace will be closed until further notice due to “the threat of intervention being prepared in a neighboring country." The spokesperson warned that any airspace violation will be met with "an energetic and immediate response." At least 3,000 Nigerien troops have since been moved from the northern Agadez region to the country's southern border with Nigeria.

Various sources told ABC News on Monday that an American delegation was currently in the Nigerian capital of Abuja to discuss a strategy to avoid neighboring Niger being overtaken by the Wagner Group, a Russian paramilitary organization, which could destabilize the entire region.

Bazoum's government has been a top ally to both the U.S. and Europe in the fight against violent extremists linked to al-Qaida and the Islamic State group in Africa's Sahel region. The U.S. Department of Defense said it has provided $500 million in military assistance to Niger since 2012, "one of the largest" security assistance and training packages in sub-Saharan Africa.

There are currently 1,100 U.S. military personnel in Niger as part of a long-running counterterrorism mission that trains the Nigerien military and runs drone operations from a large base in the northern city of Agadez, located in the Sahara desert. Those operations have been suspended in the wake of the apparent coup, namely the drone activity since Niger's airspace has been closed below 24,000 feet.

Other countries in the region, including Burkina Faso and Mali, have ousted the French military and instead enlisted the help of Wagner. In a voice message posted July 27 on social media channels linked to Wagner, the group's founder, Yevgeny Prigozhin, appeared to endorse the coup in Niger and offer the services of his fighters to the junta.

So far, there has been no indication that Prigozhin's mercenaries have arrived in Niger, but the U.S. Department of State is aware of unverified reports that leaders of the Nigerien junta have traveled abroad to seek assistance from Wagner, according to Miller.

While the U.S. has freezed its funding to Niger amid the apparent coup, Miller said money could start flowing again as soon as Bazoum is back in control.

"That assistance will affect development aid to the government, security aid to the government. It's a significant amount," he told reporters on Monday. "I don't have a number because it's a pause, and it's a pause that we would hope would be reversed if the junta leaders would step aside and restore constitutional order."

"As we've made clear, hundreds of millions of dollars are at stake," he added.

ABC News' Luis Martinez, Emma Ogao and Joe Simonetti contributed to this report.