WASHINGTON - President Barack Obama on Friday announced the nomination of US Senator John Kerry to replace Hillary Clinton as secretary of state, calling him the "perfect choice" to guide American diplomacy in the years ahead.

Obama settled on Kerry, chairman of the Senate Foreign Relations Committee and the 2004 Democratic presidential candidate, after UN Ambassador Susan Rice withdrew from consideration last week. He said he expected quick Senate confirmation of the Massachusetts lawmaker.

"As we turn the page on a decade of war, he understands that we have to harness all elements of American power," Obama said at the White House.

Even as Obama put in place one important piece of his revamped national security team, he held off on naming a new defense secretary. The delay comes in the face of a growing backlash from critics of former Republican Senator Chuck Hagel, considered a leading candidate to replace Leon Panetta at the Pentagon.