President Barack Obama updated the nation Saturday on the U.S. military mission in Libya, and while he refrained from discussing regime change, he said the effort is part of a larger strategy of holding Libyan leader Moammar Gaddafi and his government accountable for a violent crackdown on political opponents.

The president used his weekly address to report “important progress” by an international coalition in enforcing a no-fly zone over the North African country, and the White House announced Friday night that Obama would provide further updates in a speech at 7:30 p.m. Monday at the National Defense University in Washington, D.C.

Obama also organized a last-minute Congressional briefing about the situation. A bipartisan, bicameral group of Members gathered in the White House Situation Room for the briefing or participated by phone. Because secure phone lines could not be arranged, some classified information was not shared, Politico reported.

A classified Congressional briefing is scheduled for Wednesday at the Capitol Visitor Center auditorium.

In response to the crackdown, the United Nations Security Council voted March 17 to approve a no-fly zone to protect Libyan civilians. An international coalition led by the United States began enforcing the zone last Saturday, but U.S. officials were quick to say that the U.S. military would hand off primary responsibility within days. They announced Friday that a deal had been reached for NATO to take over all aspects of the mission.

Lawmakers from both parties have made their discomfort with the mission clear in the past week and criticized the administration for not seeking Congressional approval.

Obama defended his military decision Saturday.

“Make no mistake, because we acted quickly, a humanitarian catastrophe has been avoided and the lives of countless civilians — innocent men, women and children — have been saved,” he said.

He also emphasized the transition to NATO control of the mission.

“As I pledged at the outset, the role of American forces has been limited,” he said. “We are not putting any ground forces into Libya. Our military has provided unique capabilities at the beginning, but this is now a broad, international effort.”

Critics have contended that the mission lacks clarity, particularly because Obama has called for an end to Gaddafi’s power, while the U.N. Security Council resolution did not mention regime change.

Obama scaled back Saturday.

“Our message is clear and unwavering,” he said. “Gaddafi’s attacks against civilians must stop. His forces must pull back. Humanitarian assistance must be allowed to reach those in need. Those responsible for violence must be held accountable. Moammar Gaddafi has lost the confidence of his people and the legitimacy to rule, and the aspirations of the Libyan people must be realized.”

Obama told lawmakers during the White House briefing Friday that there are no plans to use the U.S. military to assassinate Gaddafi, Politico reported. Rep. Dutch Ruppersberger (D-Md.) told Politico that Obama gave no timeline for U.S. involvement in the operation.

The White House said in a statement Friday that Obama took questions from lawmakers during the briefing. Speaker John Boehner (R-Ohio), House Majority Leader Eric Cantor (R-Va.), House Minority Leader Nancy Pelosi (D-Calif.), House Minority Whip Steny Hoyer (D-Md.), Senate Minority Leader Mitch McConnell (R-Ky.) and Senate Minority Whip Jon Kyl (R-Ariz.) were among the lawmakers who participated, either in person or by phone.

Also participating were Senate Armed Services Chairman Carl Levin (D-Mich.) and ranking member John McCain (R-Ariz.), Senate Foreign Relations Chairman John Kerry (D-Mass.) and ranking member Dick Lugar (R-Ind.), Senate Intelligence Chairman Dianne Feinstein (D-Calif.) and ranking member Saxby Chambliss (R-Ga.), Senate Appropriations Chairman Daniel Inouye (D-Hawaii) and ranking member Thad Cochran (R-Miss.), House Armed Services ranking member Adam Smith (D-Wash.), House Foreign Affairs Chairwoman Ileana Ros-Lehtinen (R-Fla.) and ranking member Howard Berman (D-Calif.), House Intelligence Chairman Mike Rogers (R-Mich.) and ranking member Dutch Ruppersberger (D-Md.), and House Appropriations Chairman Hal Rogers (R-Ky.) and ranking member Norm Dicks (D-Wash.).

White House Chief of Staff William Daley, National Security Adviser Tom Donilon, Secretary of State Hillary Rodham Clinton, Chairman of the Joint Chiefs of Staff Adm. Mike Mullen and Gen. Carter Ham, who leads the U.S. Africa Command, were also involved.