The Afghan government said Friday it would not be bullied by the United States into quickly signing a security agreement, stoking tensions that could unravel plans to keep thousands of U.S. troops in Afghanistan after 2014.

One day after Afghan President Hamid Karzai shocked the Obama administration by telling an assembly of tribal elders and activists that he would not sign the bilateral security agreement until spring, he resisted calls to reconsider his timetable. Through a spokesman, Karzai said Afghans would decide the matter on their own terms and thathe has no plans to sign the accord until after the country elects a new president on April 5.

“Security, peace and good elections are the key to the signing” of the agreement, said Karzai’s chief spokesman, Aimal Faizi. He noted that the gathering of 2,500 Afghan elders and civic leaders, known as a loya jirga, is considering the agreement. “Let's wait and see the will of the people of Afghanistan in the loya jirga,” Faizi said.

In Washington, the White House signaled that there is little flexibility in its stance. Press secretary Jay Carney said the agreement under consideration by the loya jirga is the administration’s “final offer.” If not enacted by the end of the year, Carney said, it “would be impossible for the United States and our allies to plan for a presence post-2014.”

While most U.S. forces are expected to leave Afghanistan by the end of next year, the White House has been pushing to keep an estimated 5,000 to 10,000 troops in the country for counterterrorism missions and to help train and equip the Afghan military. Despite months of tense negotiations, Karzai’s views about the matter continue to shift almost daily, causing confusion both in Washington and in Kabul about whether such a deployment is possible.

Compounding the headaches for the White House, Karzai also issued a statement blaming the U.S. military for the deaths of two Afghan civilians in a raid on a house this week. Karzai said the incident threatens to derail the loya jirga, which is designed in part to gauge sentiment about basing some U.S. troops in Afghanistan after 2014.

“The government of Afghanistan for years has demanded an end of operations by foreign troops against the homes of Afghan people,” Karzai said in the statement. He added that the loya jirga needs to decide whether it wants “rogue acts by American forces” to continue.

A coalition spokesman confirmed the incident that occurred in Nangahar province on Tuesday, but described the men as “armed insurgents.”

Coalition commanders are furious, saying Karzai is making up allegations of civilian casualties for “political purposes.” They noted 100 Afghan soldiers and 17 coalition advisers took part in the mission that resulted in the two deaths.

Karzai’s accusations underscored the strain between the two governments, despite hopes that months of talks would culminate this week in the basis for a long-term partnership. Instead, the week ended as it began, with Karzai and Secretary of State John F. Kerry talking by phone to try to resolve their differences.

In a news conference last Saturday, Karzai said he was satisfied with the agreement, which would allow the United States to maintain nine bases in Afghanistan for at least 10 years.

By Monday, however, the talks were reported to have broken down over Karzai’s concerns that the agreement allowed U.S. troops to enter the homes of Afghans.

To help resolve the impasse, Karzai requested a letter from President Obama with personal assurances that controversial “night raids” would be rare.

Obama sent the letter late Wednesday, and Karzai told the loya jirga Thursday that he supported an extended U.S. presence.

But by also announcing that he would not sign the accord until April, Karzai apparently hoped to drag out the process to boost his political standing, analysts said.

If he could put off a final decision until spring, Karzai would retain power and stature that might otherwise wane as 11 candidates campaigned to replace him. Some analysts said Karzai also may be trying to get the U.S. government more involved in the election, perhaps allowing him to play a larger role in trying to broker its outcome.

“Karzai wants to use this as political pressure on the United States, so it backs his favorite presidential candidate,” said Abdul Jabaar Shelgarai, a former parliamentarian who is attending the loya jirga.

Nick Mills, a Boston University professor who wrote a book on Karzai, agreed that the Afghan president hopes to remain “the kingmaker.”

But Mills said he suspects that Obama’s letter, which stopped well short of an apology for misdeeds by U.S. forces in Afghanistan, triggered Karzai’s decision not to sign the agreement until April.

“Afghan politics are very personal, and I think he wanted a heartfelt letter from Obama and he didn’t get it,” Mills said. “So he said, ‘All right, we are going to call your bluff.’ ”

Still, with billions of dollars of future U.S. aid for the Afghan military potentially at stake, some loya jirga delegates are concerned by Karzai’s stance. Even one of Karzai’s brothers, Mahmoud Karzai, is baffled.

“We are in favor of its signing very soon, since it is not clear what will happen tomorrow in Afghanistan,” he said while attending the loya jirga.

He and others fear that the delay will give hard-line Islamist politicians more time to scuttle the U.S.-Afghan plan.

It was not clear whether Karzai would sign the agreement after the election or leave the matter to his successor, who then could demand a new round of negotiations with the U.S. government. But Faizi noted that it is still uncertain whether the agreement would be supported by the loya jirga, which is expected to reach a decision by consensus. The Afghan parliament also has to vote on the accord.

Several delegates at the assembly, which is being held in a large tent at Kabul Polytechnic University, said Friday that they have concerns about provisions of the agreement that give U.S. troops immunity for crimes on Afghan soil.

“For us, it is important that the U.S. respects our laws and sovereignty,” said Azizur Rahman, a delegate from Badakhshan province. “After being given a draft of the document, we do not see much respect for our laws.”

Karen DeYoung and Anne Gearan in Washington contributed to this report.