Senate begins debate on Trump's 'big, beautiful bill'

Defense Secretary Pete Hegseth and Joint Chiefs of Staff Chairman Gen. Dan Caine were in the Situation Room as Iran carried out an attack on a U.S. military base in Qatar, a senior Department of Defense official told ABC News.

The president was inside the Oval Office when Iran launched its retaliatory strike on the U.S. base in Qatar; a senior administration official told ABC News. The president received his national security briefing in the Oval Office, as listed on his public schedule.

Caine and Hegseth tracked the developments in the Situation Room along with other senior officials, according to a senior administration official.

Members of the president's national security team circled in and out of the Oval Office throughout much of today to provide updates, the official said.

--Editor's note: This has been corrected to reflect that President Trump was in the Oval Office during the Iranian attack.

Senate Majority Leader John Thune, R-S.D., said lawmakers will stay in Washington until the chamber passes a megabill to fund much of President Donald Trump's domestic policy agenda. Congress was set to be on recess the week of July 4.

"Senators return to Washington today and we will remain here until this reconciliation bill is passed. By placing it on President Trump's desk by the 4th of July, we will be ensuring that future generations of Americans can live in safety and prosperity," Thune wrote on X on Monday morning.

His comments come after the "One Big Beautiful Bill Act" was carefully scrutinized by Senate Parliamentarian Elizabeth MacDonough over the weekend for possible violations of the Senate's rules. This review, called the Byrd Bath, is still underway in the Senate.

President Donald Trump is scheduled to host a closed meeting with his national security team on Monday as the administration prepares for possible Iranian retaliation following this weekend's U.S. attacks on Tehran's nuclear network.

The meeting will take place in the Oval Office at 1 p.m. ET, according to the president's public schedule.

-ABC News Michelle Stoddart

Following the U.S. military strike on Iran, Trump publicly praised what he called "great unity" within the Republican Party and shifted his focus to the administration's next legislative priority.

“Great unity in the Republican Party, perhaps unity like we have never seen before. Now let’s get the Great, Big, Beautiful Bill done,” Trump wrote on social media. “Our Country is doing GREAT. MAGA!”

The post was the president’s first public comment since his address to the nation about the Iran attack on Saturday evening. The administration is aiming to pass the president's tax legislation ahead of the self-imposed July Fourth deadline.

-ABC News’ Kelsey Walsh