Senate Democrats joined Republicans Thursday in questioning the Obama administration's handling of the fatal Sept. 11 attack on the U.S. consulate in Libya and why the administration refused for days to acknowledge that it was a terrorist attack linked to al Qaeda.

The Senate Foreign Relations Committee, chaired by Sen. John Kerry, D-Mass., circulated a bipartisan letter addressed to Deputy Secretary of State Thomas Nides, asking for an "accounting of the attacks against U.S. missions in Egypt, Libya and Yemen," according to a copy obtained by The Washington Examiner.

The lawmakers are also demanding to know whether the administration had any advance warnings of the Libyan attack and, if so, whether it had shared that information with U.S. personnel on the ground.

The letter marks the first time congressional Democrats have so directly expressed their dissatisfaction with the administration's response to inquiries about the attacks, which resulted in the death of Ambassador Chris Stevens and three others and raised questions about U.S. security throughout the Middle East and Northern Africa.

A Kerry aide confirmed that the committee intended to enlist the support of Republicans and Democrats and said the letter would likely be sent Friday. Another aide told The Examiner that the panel's 10 Democrats and nine Republicans plan to sign it.

President Obama came under intense criticism because the administration's explanation for what happened at the U.S. consulate in Benghazi kept changing. For days, the administration insisted to the public and Congress that the attack was a spontaneous reaction to an American-made anti-Muslim video. As recently as Tuesday, in an address to the United Nations, Obama was blaming the video for inciting the attack.

But as evidence came to light showing that mortar rounds had been fired into the U.S. compound and that the attack had been carefully planned, the administration's explanation changed. Secretary of State Hillary Clinton first suggested in a high-level meeting at the U.N. that there could be a link between al Qaeda and "other violent extremists" and the attack in Benghazi.

On Thursday, the Pentagon confirmed that the attack was the work of a terrorist organization and not related to the anti-Muslim video.

"It was a terrorist attack," Defense Secretary Leon Panetta said at a news conference.

Until the Sept. 11 attack in Libya, Obama had enjoyed a string of national security achievements, including the killing of Osama bin Laden and the winding down of wars in Afghanistan and Iraq. Republicans were quick to question the administration's handling of the situation while Democrats charged that the criticisms were politically motivated.

The Obama administration clearly had been hoping that the Libya attack would fade in the public's consciousness, said James Carafano, a defense expert at the conservative Heritage Foundation. With congressional Democrats now also questioning how events unfolded, however, that's not likely to happen.

"Their hope was that on Monday, when the facts started to come out, everyone would have moved on, and that was a miscalculation on their part," Carafano said. "The one thing you can't do is have people intentionally lying to Congress or withholding information from Congress and then think you are not going to pay a price for that."