California Rep. Ellen O. Tauscher confirmed Wednesday that she has accepted the offer to serve as undersecretary of State for arms control and international security.

Tauscher said in a statement that Secretary of State Hillary Rodham Clinton last week offered the position to Tauscher.

“While her offer is both generous and flattering, I did not take the decision lightly. I accepted it after much soul searching and long discussions with my family and friends,” Tauscher said. She cited a desire to continue working to eliminate nuclear weapons.

Tauscher said the confirmation process for senior government posts “is fraught with uncertainty” and affirmed her commitment to district representation during the potentially lengthy procedure.

If nominated and confirmed by the Senate, Tauscher will leave Congress after a little more than a dozen years and put to a new use her expertise in defense issues.

That move also would open up a subcommittee chairmanship; Tauscher heads the Armed Services Committee’s Subcommittee on Strategic Forces.

Tauscher, a Democrat from San Francisco’s East Bay suburbs, also is chairwoman and a charter member of the New Democrat Coalition, a group of pro-business moderates. The coalition also will have to choose a new chief for that post.

A New Jersey native, she was a Wall Street stockbroker and investment banker until her relocation in 1989 to California.

Until April 2007, she also belonged to the “Blue Dogs,” a coalition of fiscally conservative congressional Democrats.

The San Francisco Chronicle once called her “about the closest thing the Bay Area has to a Republican.” That drew criticism from some in the more liberal wing of the party, but Tauscher never faced a serious challenge for renomination.

A special election will be required if Tauscher vacates the 10th District seat in California to become the nation’s top arms control diplomat. But the district’s strong Democratic leanings suggest that President Obama would not be putting Democratic control of the seat at serious risk. District voters favored Obama over Republican John McCain by 65 percent to 33 percent in the 2008 presidential election.

Tauscher won a hard-fought and narrow victory in 1996 over Republican incumbent Bill Baker, and took a modest 53 percent in each of her first two re-election contests.

But aided by a favorable redistricting plan prior to the 2002 election and by the general decline of Republican Party fortunes in California over the past decade, Tauscher coasted to easy victories in her last four contests.