WASHINGTON — The country's top mine-safety regulator will stay on the job despite the expiration of his temporary appointment as assistant labor secretary for mine safety and health.

President Bush designated Richard Stickler as acting head of the U.S. Mine Safety and Health Administration on Friday, only a few days after the expiration of his recess appointment.

The Senate could limit his service as acting leader to 210 days. The White House has renominated him for the permanent position.

The Democratic-controlled Senate has so far refused to approve his nomination. Democratic senators have said Stickler spent too many years as a coal-mining executive and failed to demonstrate that safety is his priority.

Stickler, the government's public face during the Crandall Canyon Mine disaster in Utah, took over the $340 million agency in late 2006 as a result of an appointment Bush made while Congress was out of session.

He inherited an understaffed agency that was facing new mandates following the coal industry's deadliest year in more than a decade. Forty-seven coal miners died on the job in 2006, the year he came aboard.

"MSHA's mission is to help ensure that each and every miner comes home safe after each and every shift, and with Richard's continued leadership and the diligence of everyone at MSHA, miner safety will continue to advance," Labor Secretary Elaine Chao said in a message to MSHA employees.

Stickler regularly appeared before TV cameras in August when six miners died in a cave-in at the Crandall Canyon Mine in central Utah's Emery County.

Ten days later, three men trying to clear rubble died in another collapse caused by a mountain "bounce," pressure on pillars supporting the mine.

"I thought we had ground control in place that would protect those miners," Stickler said in October.

"Knowing what I know today, I would not have allowed that activity, because we ended up with three more miners killed," he said.

His low-key style during media briefings was dramatically different than the emotional, aggressive outbursts from mine co-owner Bob Murray.

A panel appointed by Utah Gov. Jon Huntsman Jr. is studying whether the state should regulate mine safety. Coal companies are opposed.

"Certainly two eyes are better than one. ... I don't think there's any problem with that," Stickler said.