BRUSSELS -- A senior U.S. diplomat has called on the Taliban to seize a "moment of opportunity" to open formal peace talks with the Western-backed Afghan government and negotiate an end to the 17-year conflict.

Alice Wells, the U.S. principal deputy assistant secretary of state in charge of South and Central Asian affairs, told RFE/RL that the "door had opened" for a possible peace settlement with the Taliban following President Ashraf Ghani's offer of unconditional talks in February and an unprecedented cease-fire in June.

"The Afghan government is ready," Wells told RFE/RL on November 29 in Brussels, a day after she attended a UN-sponsored two-day conference on Afghanistan in Geneva. "The Afghan people, and by that I mean the Taliban also, are ready. It's a question of whether the Taliban leadership is prepared to take up this offer."

Zalmay Khalilzad, an Afghan-born former U.S. ambassador to Kabul and Iraq, was appointed in September to the U.S. State Department team that is leading the reconciliation effort and peace talks with the Taliban.

Khalilzad, who has held several rounds of preliminary talks with Taliban officials in Qatar, told reporters in Kabul this month that he was optimistic a peace deal with the militants could be reached before the presidential election in Afghanistan in April 2019.

'Moment Of Opportunity'

Wells, who met with Taliban representatives in Qatar in July, said there was no deadline but "there is a sense of urgency because we think this is a moment of opportunity."

Ghani, speaking in Geneva on November 28, said his government had formed a 12-strong team to negotiate peace with the Taliban, but he warned that any deal must fulfill certain conditions, including respecting the constitutional rights of women.

In February, Ghani offered to allow the Taliban to establish itself as a political party and said he would work to remove sanctions on the militant group, among other incentives, if it joined the government in peace negotiations. In return, the militants would have to recognize the Kabul government and respect the rule of law.

The Taliban has refused to deal directly with Kabul, saying they would negotiate only with the United States. The militants have also said NATO forces must withdraw from Afghanistan before negotiations can begin.

Wells said the militants were "suffering enormous casualties" and "there's war fatigue among the Taliban."

In June, the government and Taliban declared a three-day cease-fire coinciding with the Eid al-Fitr holiday, the first ever cessation of hostilities between the warring sides.

Wells said the cease-fire demonstrated that the sides want to "find a way to live in peace."

"They've always said publicly that they seek peace and they don't seek to dominate Afghanistan as they did in leading up to 2001," said Wells, referring to the Taliban, who were in power from 1996 until the U.S.-led invasion in 2001. "Let's test that proposition about whether or not they're prepared to actually sit and negotiate a political solution."

Efforts to open peace talks with the Taliban come as Afghan security forces struggle to fend off attacks from the militants, who control more territory than at any time since 2001.

Afghan forces are suffering record casualties, with Ghani saying that nearly 29,000 Afghan police and soldiers have been killed in the country since the start of 2015 when Afghan troops took over primary responsibility for security.

During the same period, 58 American had been killed, he said.

With reporting by RFE/RL correspondent Rikard Jozwiak in Brussels