Obama: US must show restraint abroad
President Barack Obama has promised a new US foreign policy based on "collective action" with allies abroad.
The US would still lead, he told graduates at the US Military Academy at West Point, New York, but would avoid the "costly mistakes" of the past.
He announced a $5bn (£3bn) fund to fight global terror and promised the US "must not create more enemies than we take off the battlefield".
Under attack for a weak foreign policy, he hailed progress in Ukraine and Iran.
"Sceptics often downplay the effectiveness of multilateral action. For them, working through international institutions, or respecting international law, is a sign of weakness. I think they're wrong."
The end of the combat mission in Afghanistan at the end of the year would free up resources to tackle emerging threats elsewhere, such as a new $5bn "terrorism partnership fund" to help other countries fight extremists.
Katty Kay, BBC News, Washington
In his 2009 Nobel Peace Prize acceptance speech, Barack Obama shocked Europeans with his stress on the justification of US military force. Today there is a very different emphasis.
Instead, Mr Obama focused on US-led international action - diplomatic efforts in Iran and rallying the world to put pressure on Russia for their actions in Ukraine, despite an unclear outcome there. The US president doesn't discount unilateral force entirely, but argues for the strength of other methods, especially led by the US.
But Mr Obama ducks the trickiest moment of his foreign policy - the red line in Syria and the decision to go to Congress for a vote on force, which ultimately fell apart. This is unsurprising, as the American public has zero interest staying a day longer than planned in Afghanistan, much less committing to another large-scale military mission.
The speech reflects the confusion of a country that is fed up with intervention but still likes the idea of being the world leader.
The money would go towards missions such as training security forces in Yemen, supporting a multinational force to keep the peace in Somalia, working with European allies to train a functioning security force in Libya, and helping French operations in Mali, he said.
Turning to the civil war in Syria, he promised to "ramp up support" for those in opposition to the regime of President Assad, although he did not give details about what that would mean in practice.
His speech attempted to recast US foreign policy as one which would use military force when necessary but primarily acts on a platform of international consensus.
"We must broaden our tools to include diplomacy and development; sanctions and isolation; appeals to international law and - if just, necessary, and effective - multilateral military action.
"We must do so because collective action in these circumstances is more likely to succeed, more likely to be sustained, and less likely to lead to costly mistakes."
In the wide-ranging address to West Point graduates Mr Obama touched on a range of foreign policy issues, such as:
- "a strategy that involves invading every country that harbours terrorist networks is naïve and unsustainable"
- small-scale capture and drone operations by the US military would continue to be used, but with increased transparency
- US leadership had helped bring Iran to negotiate on nuclear issues and isolated world opinion against Russia in the Ukrainian crisis
- praise for the United Nations and Nato, which he said was "the strongest alliance the world has ever known"
- "American influence is always stronger when we lead by example", he said, while criticising domestic politicians for denying climate change and refusing to sign a UN maritime treaty
- a continued push to close the US military prison at Guantanamo
- US should focus on development and education as "no American security operation can eradicate the threat posed by an extremist group like Boko Haram"
The address is the first of a series of speeches from the president about foreign policy over the next 10 days, in an attempt to respond to critics who say current US foreign policy is weak.
On Wednesday, the top Republican on the Senate's foreign relations panel said there was "an extreme indecisiveness and cautiousness" about Mr Obama "that just worries people".
"I'm not for policing the world but I do think that our lack of leadership has created a vacuum and I think that into that vacuum problems are being created," Senator Bob Corker said.