NEW YORK — Recently sworn-in U.S. citizen Craig Ferguson is being embraced by his new countrymen: The late-night comic hit a ratings milestone last week with his first victory over NBC's Conan O'Brien.

The CBS "Late Late Show" averaged more viewers than O'Brien's "Late Night" (1.88 million to 1.77 million) for the first week during which they each competed with all-original shows since Ferguson started in January 2005.

It caps a slow and steady climb for Ferguson and raises a red flag for future "Tonight" show host O'Brien, although NBC says it is still happy with O'Brien's audience.

"He's getting looser and looser all the time and for the last few months it's clear that he's having such a good time that you can't resist it as a viewer," said veteran late-night hand Peter Lassally, Ferguson's executive producer.

Ferguson, a Scotsman, passed an American citizenship test and was formally sworn in on Feb. 1. He'll be host of the annual White House correspondents' dinner in Washington later this month, a high-profile gig for a comic.

Although Ferguson had slowly become more competitive with O'Brien in the ratings, the writers strike was crucial to the surge, said producer Michael Naidus.

"It was a tough thing but for us it just let us play with the show in a looser way," Naidus said. "We threw out everything and now just have our writers doing a comedy show."

The strike also put a brighter spotlight on late-night programming and Ferguson benefited from the attention, with correspondents from newspapers and magazines writing flattering stories about him, Naidus said.

NBC acknowledged Ferguson's victory but noted O'Brien — the designated successor to Jay Leno when Leno steps down next year — still led among viewers aged 18-49, the demo-graphic the network bases its advertising sales on. Among the younger half of that demographic, O'Brien gets more viewers than David Letterman, NBC said.