Afghan President Hamid Karzai is continuing to resist Obama administration efforts to persuade him to sign an agreement as soon as possible on the parameters of a post-war relationship.

The U.S. Ambassador to Afghanistan, James Cunningham, has privately warned the Obama administration that Karzai is unlikely to sign the pact on Washington's timetable and is leaning against agreeing to it before a presidential election scheduled for April, according to a report in the Washington Post that cited a classified cable from Cunningham to State Department officials.The Pentagon and the State Department have repeatedly warned Karzai that waiting to sign the agreement would make it difficult to plan for a residual U.S. presence in the country by the end of the year and could result in a hasty troop withdrawal.

State Department spokeswoman Jen Psaki Friday declined to comment on or confirm the existence of the cable. She also delivered a stern warning to Karzai, threatening to withdraw all U.S. and NATO troops if the agreement is not signed soon.

“If we cannot conclude [the agreement] promptly, then we will initiate planning for a post-2014 future in which there would be no U.S. and NATO troop presence in Afghanistan,” she said.

“We recognize that at this time it is up to President Karzai to determine what is in Afghanistan's best interest, and we continue to work on the ground with President Karzai and his team on encouraging them to sign...”

The Obama administration already has extended the deadline for signing the document by several months, and the White House earlier this week again urged Karzai to quickly approve the document, saying it must be signed within “weeks, not months.”

In a speech in late November, Karzai publicly said he would never sign the agreement and wanted to allow his successor to do so.

With tensions between Karzai and U.S. officials at a all-time high, the Afghan leader Thursday dealt a separate blow to the relationship.

His government decided to release 73 terrorism suspects held in a prison outside Kabul. The U.S. military had turned over control of the prison to the Afghan government earlier this year with the understanding that the Afghan government would try the detainees in its courts.

Republicans in Congress, including Speaker John Boehner of Ohio and Sen. John McCain of Arizona, this week have criticized the Obama administration's handling of the post-war relationship with Iraq and failing to counter Iran's influence in that country. Sectarian violence and a resurgence of al Qaeda control over major cities in key regions have Iraq teetering on the brink of civil war.

Members on both sides of the aisle worry the U.S. is now losing any ongoing influence it could have in the future of Afghanistan and the country could return to Taliban control and serving as a haven for al Qaeda.

McCain and Sen. Lindsey Graham, R-S.C., were particularly concerned about the release of 72 prisoners in the prison outside of Kabul.

“All we are asking is to follow the Afghan rule of law and not allow extrajudicial releases,” they said in a joint statement Thursday night. “We made it clear to President Karzai last week in Kabul that the release of these detainees in this way would undermine the rule of law in Afghanistan and have a negative impact on our bilateral relationship in the Congress.”

“We are in contact with our military and civilian leaders in Afghanistan and will determine what course of action is appropriate once we have received additional information,” they said.