President Obama has defended U.S. involvement in Libya, saying the international operation has protected thousands of people in the North African country.

Mr. Obama said he did not violate the War Powers Resolution, a U.S. law that requires congressional approval within 60 days if U.S. forces are involved in hostilities.

He said Libyan leader Moammar Gadhafi was threatening to massacre his people, and the United States, as part of an international coalition, took out Libyan air defense systems so humanitarian assistance could be provided. He said pressure is increasing on the Libyan leader, or as he put it, “the noose is tightening.”

He said he addressed the American people on Libya and briefed members of Congress and has done “exactly” what he said he would. He said the operation is limited in time and scope, and there have been no U.S. casualties and no risk of additional escalation.

He said the narrow mission has been carried out in “exemplary fashion.” But he said questioning whether he needs congressional approval for the mission has become a popular topic among some lawmakers.