Ignoring a White House veto threat, the House on Wednesday was moving toward passage of a bill designed to tighten mine safety enforcement in the wake of several deadly accidents over the past two years.

The legislation is a follow-up to a major mine safety law enacted 18 months ago after a January 2006 explosion in West Virginia’s Sago Mine that killed 12 workers. That law required mine owners to install wireless communications equipment and tracking devices within three years. It also raised maximum fines for accidents and gave the government the power to close mines when operators don’t pay fines.

Democrats contend the new law is too weak; industry officials say they are struggling to implement the broad changes it requires.

The bill before the House was introduced by Rep. George Miller, D-Calif., less than two months before August’s cave-in at the Crandall Canyon coal mine in Utah, which killed six miners and three rescue workers. It would shorten to 15 months the deadline for installation of new communications equipment, increase oversight of “retreat mining” — the type at Crandall Canyon — and boost the enforcement authority of the Mine Safety and Health Administration.

Miller said the Bush administration has a “horrendous” track record on mine safety, and has failed to move aggressively to step up inspections and enforce the 2006 law.

In a policy statement, the White House said the bill “would place in jeopardy meaningful achievements and efforts currently under way as a result of those measures” and would “impose burdensome and unrealistic time requirements.”

Rep. Howard P. “Buck” McKeon, R-Calif., slammed the bill as “premature at best,” adding it “ignores the progress that has been made.” He urged adoption of a GOP substitute that would strip the new fines, earlier timelines and stricter safety requirements from the bill.