By Michelle Nichols

UNITED NATIONS (Reuters) - Most of the 47 countries that pledged support to U.N. peacekeeping at a summit led by U.S. President Barack Obama have taken steps to lock in the commitments, according to a draft report seen by Reuters, but several of them - including Spain - are lagging.

The U.S.-led push for more U.N. troop options comes amid allegations of misconduct and sexual abuse by U.N. peacekeepers in Central African Republic. Officials and diplomats said it was hoped surplus troops would allow the U.N. to exercise more discretion with its 16 current missions.

The United Nations is using some of the new troops on offer as leverage to put pressure on poor-performing units, a U.N. diplomat said, citing the repatriation of hundreds of Democratic Republic of Congo troops from Central African Republic after sexual abuse accusations.

The U.N. draft report on the status of the pledges made at Obama's September summit showed some of the support promised by 10 countries had already been deployed to U.N. missions in Mali, South Sudan, Congo and elsewhere.

More than 40,000 troops and police, as well as helicopters, military engineering companies and field hospitals, were pledged during Obama's summit of world leaders at the United Nations in a bid to boost the capacity of peacekeeping.

The draft report on the pledges will be given to member states but will not be made public, and could change before it is distributed, said a U.N. diplomat familiar with the report.

"There is substantial progress but we want all countries to follow through as soon as possible," said a U.S. official on condition of anonymity.

Spain had pledged troops, helicopters and intelligence, surveillance and reconnaissance capabilities to the peacekeeping mission in Lebanon.

"But they subsequently communicated to the U.N. that those were contingent on the U.N. selecting a Spaniard as force commander, at which the U.N. balked," a U.N. diplomat said.

Another diplomat said Spain completely withdrew its pledge after the U.N. chose General Michael Beary of Ireland.

Spain's U.N. mission declined comment.

Uganda, Georgia, Azerbaijan, Colombia, Norway, Spain, Brazil and Vietnam have not followed through on all or part of their pledges, said the U.N. draft report.

U.S. Joint Chiefs of Staff Joe Dunford and Deputy British Chief of Defence Staff General Gordon Messenger will host a closed-door meeting on Friday at U.N. headquarters to assess progress on realizing the pledges.

Washington pays for about 28 percent of the $8.2 billion U.N. peacekeeping budget.

(Additional reporting by Louis Charbonneau at United Nations; Editing by Matthew Lewis)