Obama Says 'Official' Explanation Coming 'Shortly' on Alleged Sestak Job Offer

May 23: In this photo provided by CBS, Rep. Joe Sestak, D-Pa., appears on CBS's "Face the Nation" in Washington (AP).

President Obama said Thursday that the White House is preparing to issue a formal explanation regarding the allegation that it offered Rep. Joe Sestak a job to drop out of the Democratic primary race against Sen. Arlen Specter.

The president, addressing the matter in public for the first time since the Pennsylvania congressman leveled the claim in February, said the statement should answer questions about the claim and insisted "nothing improper" happened.

"There will be an official response shortly on the Sestak matter," Obama said, when asked about the issue by Fox News at the president's press conference. "I mean shortly -- I don't mean weeks or months. ... I can assure the public that nothing improper took place."

White House Press Secretary Robert Gibbs has also said nothing improper happened, but refused to elaborate when asked repeatedly about the charge at Thursday's briefing.

Sestak, who did not drop out and won the race against Specter last week, repeated his allegation in an interview on Sunday, but also declined to elaborate.

Rep. Darrell Issa, R-Calif., who has been leading the charge for more details on the allegation, said he hopes Obama's pending response "will detail what conversations were had with Congressman Sestak."

"If what the president said is true and nothing 'improper' took place, Adm. Sestak's credibility will be called into significant question," Issa said in a statement. "If the president's response is insufficient or contradicted, the situation will only escalate."