Obama chaired a summit of world leaders at the United Nations to garner commitments to boost the capacity and capabilities of UN peacekeeping and to allow the world body to deploy forces more rapidly if a new operation is created.
"Our goal should be to make every new peace operation more efficient and more effective than the last," Obama said.
The US ambassador to the United Nations, Samantha Power, said in addition to some 40,000 new troops and police, more than 50 countries had pledged to provide more than 40 helicopters, 15 military engineering companies and 10 field hospitals.
China made one of the biggest commitments. President Xi Jinping pledged to set up a "permanent peacekeeping police squad and build a peacekeeping standby force of 8,000 troops."
According to the UN website, the US provides 82 of the more than 106,500 people deployed on UN peacekeeping missions: 34 troops, 42 police and six military advisers. But Washington pays for more than 28% of the more than US$8.2 billion UN peacekeeping budget.
Obama said the United States would work to double the number of military advisers that it contributes to UN peacekeeping, and offer logistical support, including air and sea lifts, and training.
During a speech in Brussels in March, US Ambassador to the United Nations Samantha Power called on Europe to consider contributing more to UN peacekeeping. She said two decades ago Europeans made up 40% of UN peacekeepers, but that has fallen to about 7%.
More than a dozen European countries stepped up on September 28. British Prime Minister David Cameron pledged to send 70 troops and experts to the UN and African Union peacekeeping force in Somalia and up to 300 troops to the UN mission in South Sudan.
The top five troop- and police-contributing countries to UN peacekeeping missions are Bangladesh, Ethiopia, India, Pakistan and Rwanda.
They all made further pledges at summit on September 28.