US Secretary of State Anthony Blinken has made a blunt new push for a UN-led peace effort in Afghanistan.
In a letter to the Afghan President Ashraf Ghani, Blinken called for a 90-day reduction in violence and a transitional government formed from both sides.
Blinken also said no decision had been made about whether to stick to a planned US troop withdrawal by 1 May.
He called on President Ghani to show "urgent leadership".
Blinken's letter, a copy of which was obtained by the BBC on Sunday, reflected the difficult position the US finds itself in as it reviews whether to withdraw its last 2500 troops.
A deal struck with the Taliban during the Trump administration in February 2020 committed the US to withdrawing by 1 May, but Afghan officials fear the move would create enormous security challenges.
Blinken warned in his letter that the Taliban could make "rapid territorial gains" across the country in a "spring offensive".
He also proposed a "transitional peace government" to usher the country through this precarious period, followed by national elections, as well as a UN-led peace conference in Turkey attended by foreign ministers and envoys from Russia, China, Pakistan, Iran, India and the US.
The BBC's chief international correspondent, Lyse Doucet, describes the letter to President Ghani as "blunt" and as an effort to "step up the pressure" on the Afghan government and the Taliban.
However, the disagreement and distrust between the two sides is still wide and Afghans worry that a deal brokered in haste could quickly break down, the correspondent adds.
US-led forces ousted the Taliban from power in Afghanistan in 2001, shortly after the 11 September terror attacks.
The level of violence in the country remains high. The past year has seen a surge in targeted killings of journalists, activists, judges, and other civil society figures - killings blamed largely on the Taliban.
The planned US and Nato withdrawal has led to fears, particularly among women's rights activists, that a Taliban return to power could compromise the progress made over the past two decades.
Zalmay Khalilzad, the US diplomat spearheading the current intra-Afghan peace process, will meet Pakistani officials on Monday in Pakistan, which is widely viewed as having leverage over the Taliban.
What was the US-Taliban deal?
The Trump administration made withdrawing troops from Afghanistan a priority.
The deal signed in February 2020 said that the US and its Nato allies would withdraw all troops in 14 months if the Taliban upheld its promises, including not allowing al-Qaeda or other militants to operate in areas it controlled, and proceeding with national peace talks.
Although the Taliban, a hard-line Islamic movement, stopped attacks on international forces as part of the historic agreement, it has continued to fight the Afghan government.
As a condition of starting negotiations with the Afghan government, the Taliban also demanded that thousands of their men be released in a prisoner swap.
Direct talks then began Doha in September 2020, but a breakthrough has still not been reached.