71 killed in Israeli attack on Iran prison, official says

The White House transmitted its official notice of the U.S. strikes on Iran to Congressional Leaders in the House and Senate Monday evening.

Under the War Powers Resolution, the administration has 48 hours after an attack to notify Congress of its action. This notification arrived before the deadline.

The letter, posted to the White House's website, does not appear to provide many new details on the strike.

"I directed this military action consistent with my responsibility to protect United States citizens both at home and abroad as well as in furtherance of United States national security and foreign policy interests," President Donald Trump wrote in the letter. "I acted pursuant to my constitutional authority as Commander in Chief and Chief Executive and pursuant to my constitutional authority to conduct United States foreign relations."

Both the House and the Senate are slated to receive classified briefings on Iran on Tuesday.

-ABC News' Lauren Peller and Allison Pecorin

Vice President JD Vance reacted live to President Donald Trump's social media post announcing a ceasefire between Israel and Iran in an interview with Fox News.

"Tomorrow really is a new day -- the end of the 12-day war, the end of the Iranian nuclear program and I really do believe the beginning of something very big for peace in the Middle East," Vance told Bret Baier.

The vice president said he previewed Trump's social media post before he went on air with Fox News.

"He's been working the phones constantly -- frankly, before the 12-day war started, but certainly over the past 12 days," Vance said. "The president's been extremely clear about America's national objective -- it is to create a world where Iran cannot build a nuclear weapon."

Vance said he thinks Trump has "hit the reset button" and called the conflict "an important reset moment for the entire region."

-ABC News' Kelsey Walsh

There are no active plans for the U.S. to respond to Iran's retaliation at this time, according to a U.S. official and two sources familiar with the president's thinking.

One source cited Iran's attacks as a "failed retaliation" and said there was a growing consensus among the president's advisers that there may not need to be a response at this time.

The source stated the president feels Iran has gotten the attacks "out of their system," as Trump stated on social media Monday, but cautioned he reserves the option to change his mind.

-ABC News' Rachel Scott and Luis Martinez

President Donald Trump announced on social media that Israel and Iran have agreed to a complete and total ceasefire, set to begin in approximately 6 hours.

The agreement involves two 12-hour ceasefire periods, according to Trump:

• Iran will initiate the first 12-hour ceasefire.
• Israel will follow with the second 12-hour ceasefire.
• After 24 hours, the war will be officially declared ended.

"I would like to congratulate both Countries, Israel and Iran, on having the Stamina, Courage, and Intelligence to end, what should be called, 'THE 12 DAY WAR,'" Trump wrote on Truth Social.

-ABC News' Kelsey Walsh