By Toni Clarke

WASHINGTON (Reuters) - The Senate on Monday moved closer to confirming Dr. Robert Califf to lead the Food and Drug Administration, overriding opposition from several senators who had sought to block a vote on the issue.

In a procedural move designed to prevent the opponents from blocking the confirmation indefinitely, the Senate voted 80 to 6 in favor of limiting further debate on the matter to no more than 30 hours, meaning a confirmation vote could take place as early as Tuesday.

Democrats Edward Markey of Massachusetts and Joe Manchin of West Virginia among others had sought to block the confirmation vote citing disagreements with the FDA's process for approving opioid painkillers.

Democratic presidential candidate Bernie Sanders also placed a hold on the nomination, saying he objected to Califf's close ties to the pharmaceutical industry.

Under pressure, the FDA recently agreed to a number of changes to its opioid approval process, and said it would convene an advisory panel meeting before approving new opioid painkillers that do not include an abuse-deterrent feature.

The opponents said the measures do not go far enough and that advisory panels should be called before any opioid is approved.

"The FDA has to be the cop on the beat," Markey said.

Before the vote opponents, including Richard Blumenthal of Connecticut, took to the floor to berate the FDA for approving opioid products such as Zohydro over the objections of its advisory committee.

The FDA, Manchin added, "must break its cozy relationship with the pharmaceutical industry." He said more people die of legal prescription drug abuse in West Virginia than any other cause.

(Reporting by Toni Clarke; Editing by Eric Beech and Andrew Hay)