UNITED NATIONS (Reuters) - Some 50 world leaders, more than a third from Europe, are set to pledge thousands of troops and police, equipment or training for United Nations peacekeeping missions during a summit that will be chaired by U.S. President Barack Obama on Monday, a U.S. official said.

The United States has "significantly exceeded" its goal of garnering commitments for a surplus of 10,000 troops and police that will allow the United Nations to more rapidly deploy forces if a new operation needs to be created, the U.S. official said on Tuesday.

Amid a stream of allegations of misconduct and sexual abuse by U.N. peacekeepers in Central African Republic, he also said the surplus of troops and police would allow the world body to exercise more discretion with its 16 current missions.

"If there is a troop contingent that's committing abuses or a troop contingent that's not performing the mandate (the U.N.) can actually repatriate that contingent knowing that there are a significant number of other countries that are now willing to step in," said the official, who spoke on condition of anonymity.

During a speech in Brussels in March, U.S. Ambassador to the United Nations Samantha Power called on Europe to consider contributing more to U.N. peacekeeping. She said two decades ago Europeans made up 40 percent of U.N. peacekeepers, but that has fallen to about 7 percent.

Around 20 European leaders are expected to announce commitments at the summit on the sidelines of the U.N. General Assembly on Monday, the U.S. official said.

"European leaders will typically be announcing one or two discreet military units to go into peacekeeping in the short or medium term," he said. "I think you will especially see Europeans coming forward in areas like engineering, medical, counter-IED (improvised explosive devices), those sorts of areas which are small in numbers but outsize impact."

The U.S. official said several Latin American and Asian countries were stepping forward with commitments to make up the surplus of troops and police.

U.S. Army General Martin Dempsey, chairman of the Joint Chiefs of Staff, told dozens of U.N. ambassadors and military advisors in New York in July that the United Nations needed rapid response forces, equipment and training.

Some European diplomats have privately expressed annoyance that the United States is pushing Europe to offer more troops to U.N. missions without itself offering troops and police.

According to the U.N. website, the United States provides 82 troops, police and advisers of the more than 106,5000 deployed on U.N. peacekeeping missions. Washington pays for more than 28 percent of the more than $8.2 billion U.N. peacekeeping budget.

The U.S. official said Washington was considering increasing the number of military advisers and making available the country's "unrivalled set of airlift capabilities."

The top five troop and police contributing countries to U.N. peacekeeping missions are Bangladesh, Ethiopia, India, Pakistan and Rwanda.

(Reporting by Michelle Nichols; Editing by Toni Reinhold)