The departure of Minerals Management Service Director Elizabeth Birnbaum was announced by Interior Secretary Ken Salazar at a congressional hearing where Birnbaum had been scheduled to testify but didn't show up.
Birnbaum resigned "on her own terms and her own volition," Salazar told lawmakers.
The development came just hours before a White House press conference where Obama was set to announce strong new measures in response to the spill, including extending a moratorium on new deepwater oil drilling and canceling some planned lease sales entirely.
Birnbaum, who had led MMS since July 2009, was out after she and her agency came under withering criticism from lawmakers of both parties over lax oversight of drilling and cozy ties with industry. Salazar recently announced he was radically restructuring the agency into three separate parts.
It was a day of fast-moving developments in Washington and in the Gulf, where engineers were watching for signs of success from the latest attempt to stanch the leak five weeks into the catastrophe.
