NATO defense ministers convened a two-day meeting here Wednesday with a renewed warning that they are prepared to withdraw all of their troops from Afghanistan without a signed security agreement.

“We all know the facts,” NATO Secretary General Anders Fogh Rasmussen said as ministers moved behind closed doors. If there is no security agreement between Afghanistan and the United States, he said, there would be no NATO agreement with Afghanistan, and “there will be no NATO troops in Afghanistan after 2014.”

U.S. troops comprise about two-thirds of the international force in Afghanistan, which is now down to about 50,000 and is on its way to a complete combat withdrawal by the end of this year. That ratio would remain roughly the same under a plan drawn up by Gen. Joseph Dunford, the U.S. and NATO commander, to leave a total force of 8,000 to 12,000 behind for training and counterterrorism missions next year and possibly beyond.

President Obama on Tuesday ordered the Pentagon to begin drawing up a new plan for complete withdrawal, to be implemented if Afghanistan continues to refuse to sign a bilateral security agreement, or BSA.

Obama’s announcement was the first official confirmation of what most NATO members had assumed, as relations between the United States and Afghan President Hamid Karzai have worsened in recent months.

Now, alliance partners “want clarity” from the administration, said a senior NATO official who spoke on condition of anonymity in advance of member meetings. When they are briefed Thursday by Dunford and Defense Secretary Chuck Hagel, ministers expected to hear about the range of U.S. options under consideration, the official said.

Under a separate option favored by some in the White House, a U.S. contingent left in Afghanistan could number as few as 3,000 troops, a possibility that would likely lead other NATO members to opt out of a post-2014 force.

Afghan Defense Minister Bismillah Khan Mohammadi is also expected to brief the alliance. According to reports from Kabul, key members of Karzai’s cabinet have urged him to sign the agreement.

NATO is negotiating a separate agreement with Afghanistan but has made clear it will not be completed until after the U.S. deal is signed.

Rasmussen reinforced Tuesday’s White House statement that time remains for a new Afghan government to sign the U.S. deal following Afghan presidential elections in April.

“We stand ready to establish the training mission after 2014, but time is of the essence,” Rasmussen said. “It appears that President Karzai is not ready to sign a security agreement. We are ready to engage with a new president after the . . . elections.”

“Our preferred option is to stay” in Afghanistan, Rasmussen said. But “if we don’t have the legal framework in place, we will have to withdraw everything.”