Defense Secretary Chuck HagelChuck HagelWho will temper Trump after he takes office? Hagel: I’m ‘encouraged’ by Trump’s Russia outreach Want to 'drain the swamp'? Implement regular order MORE is turning up the heat on Afghan leaders, pressing for a final postwar plan to be in place by year's end.
"We continue to plan for a [postwar] train, assist and advise counterterrorism role" in Afghanistan, according to the Pentagon chief.
"If this issue rolls into next year, it is going to be very difficult for my responsibilities, along with our military, to go beyond just the planning stages" for an American-led postwar effort in Afghanistan.
Hagel's comments echoed those of White House spokesman Jay Carney, who also indicated time is running out for Afghanistan to approve the deal.
Postponing ratification of the postwar plan "is not practical or tenable," Carney told reporters at the White House on Friday.
The deal reached between Secretary of State John KerryJohn KerryPalestinian leader: Moving Israel embassy could jeopardize peace process UN leader willing to meet lawmakers amid push to cut funding Will Rubio vote for Tillerson? MORE and Afghan President Hamid Karzai "represents a good faith negotiated agreement and it's our final offer," according to Carney.
"It's time to get this done," he added.
But Kabul fired back at Washington's demands, telling Reuters it will ratify the postwar plan on its own timelines, regardless of the Obama administration's wishes.
"We do not recognize any deadline from the U.S. side," Karzai spokesman Aimal Faizi said Friday.
The White House and its allies in NATO "have set other deadlines also, so this is nothing new to us," according to Faizi.
The postwar plan, known inside the Pentagon as the bilateral security agreement (BSA), was presented by Karzai to the Loya Jirga, an assembly of the Afghanistan's most powerful tribal leaders, on Thursday.
The BSA would go into effect in January 2015 and last roughly a decade, should the Karzai administration and the jirga approve the plan.
However, Kabul retains the option to terminate the deal before the deal expires in 2024, according to the terms of the postwar pact.
But Karzai said on Thursday that Kabul may not ratify the BSA until after the country's presidential elections, slated for April 2014.
All American combat troops in country are slated to withdraw from Afghanistan by January 2014, three months before Afghan leaders plan to consider approval of the BSA.
That delay, according to Hagel, will only further complicate planning and coordination for an already difficult and complex U.S. postwar mission.
"I think it would put the United States in a very, very difficult position, because until we have a [BSA] that essentially gives us then the assurance that we need to go forward," Hagel.
Specifically, a delay in BSA approval ties the White House's hands in terms of finalizing troop numbers for that postwar force.
"I don't think the president is going to commit to anything" in terms of troop numbers until Kabul agrees to the BSA, Hagel said, adding "my advice to him would be to not."
The Obama White House is considering a 9,000- to 10,000-man postwar force for Afghanistan to lock in security gains by American and NATO forces in the country are maintained after the 2014 drawdown.
The American units would be part of a NATO-led postwar force that could total upwards of 15,000 Western troops, primarily used to train Afghan forces and execute targeted counterterrorism operations against the Taliban, al Qaeda and other militant extremist groups operating in the country.
Despite the pressure coming from the Obama administration, Hagel said he was confident Afghanistan's leaders would meet Washington's demands.
"We want a partnership. We want to go forward [and] I anticipate we will," he said.
—Amie Parnes contributed to this report.