WASHINGTON (AP) - Democrat Barack Obama was stumped this weekend when a woman asked him about cleanup at the nation's most contaminated nuclear area: the Hanford site in Washington state where scientists helped create the atomic bomb.

Obama admitted he didn't know much about the problem, but promised he would learn about it.

"Here's something that you will rarely hear from a politician, and that is that I'm not familiar with the Hanford site, so I don't know exactly what's going on there," Obama said Sunday at a campaign stop in Pendleton, Ore. "Now, having said that, I promise you I'll learn about it by the time I leave here on the ride back to the airport."

A spokesman for the Republican National Committee called Obama's answer proof that the Illinois senator has little understanding of issues that are important to families in Oregon and Washington. During a visit to Washington state last week, Republican John McCain said he would speed cleanup efforts at Hanford and push for technological advances in disposing of nuclear waste.

"How can Obama deliver change if he doesn't even understand what needs to be changed?" asked RNC spokesman Paul Lindsay.

Despite Obama's answer to the voter, a campaign spokesman said Monday that Obama is committed to cleaning up Hanford and other contaminated nuclear sites.

"Sen. Obama will reverse the Bush administration's budget cuts and ensure that the Hanford cleanup effort receives enough resources and support to protect area residents and businesses," said spokesman Nick Shapiro.

The federal government created Hanford in the 1940s as part of the top-secret Manhattan Project to build the atomic bomb. The government now spends about $2 billion a year to clean up the site.

The Energy Department, which manages Hanford cleanup, announced last year that it would be unable to meet a number of cleanup deadlines at the site. The agency has been in negotiations with Washington state for the past year to establish new deadlines and cleanup priorities.

Ridding Hanford of contamination has long been a priority for Washington Gov. Chris Gregoire, who championed the original cleanup pact signed by the state and federal governments in 1989 when she was director of the state Department of Ecology. A Democrat, Gregoire has endorsed Obama and is herself running for re-election.

The governor is confident that Obama will make toxic cleanup a priority, Gregoire campaign spokesman Aaron Toso said.

"We feel that an Obama White House will be much more favorable to environmental cleanup than the Bush administration," he said.

Associated Press Writer Shannon Dininny in Yakima, Wash., contributed to this story.