The new contributions will also include helicopters, engineering units and field hospitals that are desperately needed to bolster UN peace missions, said the official who asked not to be named.
More than 105,000 troops and police serve in the UN`s 16 peacekeeping missions worldwide.
The summit could provide a major boost to the United Nations, which has been struggling to persuade countries to contribute their soldiers to peace operations.
British Prime Minister David Cameron is among 20 European leaders who will be announcing concrete military and police contributions in a shift that Washington describes as Europe`s return to peacekeeping.
US Ambassador to the United Nations Samantha Power traveled to Brussels in March to ask European countries to step up their support.
Over the past two decades, European contributions to UN peacekeeping fell from 40 per cent to just seven percent, even though countries have been heavily involved in the NATO-led mission in Afghanistan.
Despite its appeal for governments to do more the United States will not significantly boost its involvement in UN peacekeeping beyond providing staff officers in missions and airlift capabilities.
There are currently 78 Americans serving in UN peace missions.
Washington however continues to be the number one financial contributor, providing 28 per cent of the UN peacekeeping budget of $8.3 billion.
The new troop commitments will come from Europe but there will be announcements from India and Japan, as well as new contributions from African countries.
Bangladesh, Ethiopia, India and Pakistan are among the top troop-contributing nations.
Boosting troop contributions will allow the United Nations to deal more effectively with a wave of sexual abuse allegations that have hit its missions, notably in the Central African Republic, the US official said.
The new commitments will give Secretary-General Ban Ki-moon the leeway to remove units whose soldiers face accusations and replace them without weakening a mission.
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