In her media briefing Thursday, U.S. State Department deputy spokeswoman Marie Harf warned unless the Bilateral Security Agreement is concluded promptly, "we will initiate planning for a post-2014 future" when there would be no U.S. or NATO troop presence in Afghanistan after the withdrawal of coalition forces by the end of this year.
Separately, a delegation of U.S. senators visiting Afghanistan urged Karzai to sign the agreement without delay. The delegations included Republicans John McCain of Arizona and Lindsey Graham of South Carolina.
The agreement was approved overwhelmingly by Afghanistan's Loya Jirga council of elders in November and was to have been signed by Karzai by the end of December. The United States has insisted the agreement must be signed so it can plan and prepare to leave some troops in Afghanistan post-2014.
Karzai, however, is seeking more guarantees, including additional assurances civilians will be protected, before approving the agreement. He also has said it should be signed only by Afghanistan's new president after the April elections.
The United States has refused to make any changes in the agreement as it took more than a year of intense negotiations just to arrive at the final draft presented to the Loya Jirga. With an agreement in place, up to 15,000 foreign soldiers would remain in Afghanistan to train the Afghan forces and conduct counter-terrorism operations.
Without a signed agreement, Afghanistan may also lose billions of dollars of international aid it badly needs to bolster its security forces.
NATO Secretary-General Andres Fogh Rasmussen has said a NATO Status of Forces Agreement cannot be signed until the agreement with the United States is concluded.
After meeting Karzai, Graham told reporters in Kabul that progress on the pact is crucial before President Barack Obama's annual State of the Union speech to the American people, the Voice of America reported.
"What is he going to tell the American people about Afghanistan? If there is no bilateral security agreement signed, he cannot commit troops in the future and Congress cannot fund," Graham said. "So, time is running out. We need to get this agreement done in a mutually beneficial way soon, or we will lose the opportunity to secure Afghanistan and we will have another Iraq in the making."
McCain said he was "confident from our conversation that the differences have been narrowed to a point where we could get them resolved in a very short time period."
Harf, in her briefing, said further delay in signing the agreement would make it "more likely" there would be no U.S. troop presence after this year.
"At this point, I would expect that as we continue to consider options to present to the president and the interagency for a post-2014 presence, we will have to increasingly factor in the lack of a BSA into that planning," she said. "We'll need to frame decisions based on our position that we can't pursue a post-2014 mission without a BSA.
"Again, this isn't an outcome we're seeking. This isn't a future we're seeking. That's why we believe it's important to get it signed as soon as possible."