Obama’s decision to send more troops to Iraq and to join air strikes on Syria has alarmed his European allies.
The US president said the United States would not tolerate further expansion of Islamic State (IS) and warned it would not be tolerated in the region.
In a speech on Sunday, Obama said the US would not allow IS to “take over the entire region”.
Obama made the comments in an address to the United Nations General Assembly in New York ahead of a speech to the Security Council on Monday.
He was responding to a vote by Russia to back a draft resolution calling for a US military action against IS.
Obama is set to travel to Brussels on Monday and to Brussels for talks with the European Union on Monday night.
European leaders are expected to push for the deployment of more American troops and to provide support to Kurdish fighters in Iraq.
Obama said he would not go “beyond the call” made by German Chancellor Angela Merkel and others.
“We will not allow the expansion or expansion of this terrorist group, and I will not permit it to take over the whole region,” Obama said.
Obama did not mention IS by name in his speech.
But in a separate statement, the White House said the military deployment in Iraq would “help the Iraqis to ensure that the fight against IS does not go on forever, but that the group does not beget more.”
The deployment of U.S. and coalition troops will ensure that our forces in Iraq will continue to be the decisive force in that fight against the Islamic State and other radical Islamic groups,” the statement said.IS has captured large parts of Iraq and parts of Syria and is now making gains against the Iraqi army and Kurdish forces.
Obama’s announcement comes as he faces pressure to take military action in Syria.
On Friday, the US Senate rejected a Republican amendment to the annual defense authorization bill that would have authorized military action over Syria.
Obama has said the administration is committed to an attack against IS in Syria, but he is under pressure from some Republicans to go further in Syria than he did last year.
Obama wants to take action against the Syrian government of Bashar al-Assad, but the US is opposed to sending troops there.
The United States has said that it will only intervene if the Syrian military attacks or violates international laws, including the Chemical Weapons Convention.