WASHINGTON — The Obama administration and House Democrats said Monday they were undecided about whether to take part in or boycott an election-year investigation by Republicans into the Benghazi attack that killed four Americans.

House Speaker John Boehner announced last week he would create a select committee to examine the response to the deadly Sept. 11, 2012, assault on the U.S. diplomatic post in Libya that killed Ambassador Chris Stevens and three other Americans. Legislative aides said a vote to authorize the panel is expected sometime this week. On Monday, Boehner said Rep. Trey Gowdy, R-S.C., would head the investigation.

The action puts President Obama’s team and House Democrats in a bind. They are concerned about what they believe will be a partisan forum for attacks on the president and his top aides ahead of crucial midterm elections in November, which could swing the Senate to GOP control. But avoiding the committee altogether means sacrificing the ability to counter Republican claims.

White House press secretary Jay Carney stressed Monday that the administration always cooperates with “legitimate” congressional oversight – including sending witnesses to hearings and providing bipartisan committees with documents. He declined to characterize whether the Obama administration would view a House select committee as legitimate or illegitimate. But he said that what Republicans have said about the committee “certainly casts doubt” about its legitimacy.

Carney also suggested the select committee was unnecessary. “One thing this Congress is not short on is investigations into what happened before, during and after the attacks in Benghazi,” he told reporters.

Boehner and other Republicans accuse the administration of misleading the American people after the attack to protect Obama in the final weeks of his re-election campaign, and of stonewalling congressional investigators ever since. They pointed to emails released only last week as further evidence of White House wrongdoing.

Rep. Steny Hoyer of Maryland, the No. 2-ranked Democrat, said he and his colleagues would first have to see the specifics of Boehner’s proposed committee before making a decision on participating in or boycotting the new probe. He said he and other party leaders would vote against establishing the committee.

“This has been seriously and thoroughly investigated,” said Hoyer.