President Barack Obama faces growing skepticism in Washington over his plan to defeat Islamic State jihadists in Iraq and Syria without U.S. ground troops, with critics blasting the strategy as unrealistic and half-hearted.

Obama's repeated vow that he will not order "boots on the ground" has infuriated Republicans in Congress, who argue that air power alone cannot roll back the IS extremists given the absence of a viable moderate rebel force in Syria and the Iraqi army's poor track record.

U.S. President Barack Obama congratulated Scotland Friday on its "full and energetic exercise of democracy," as he welcomed the result of its historic referendum rejecting independence from the United Kingdom.

"We have no closer ally than the United Kingdom, and we look forward to continuing our strong and special relationship with all the people of Great Britain and Northern Ireland as we address the challenges facing the world today," Obama said in a statement.

Warring parties in Ukraine meet on Friday to try to find a lasting solution to a brutal conflict that has killed around 3,000 people and stoked Western alarm about Russia's territorial ambitions.

The talks take place in Minsk two weeks since a fragile European-brokered ceasefire aimed at halting five months of bloodshed was agreed in the Belarussian capital with Moscow, Kiev and pro-Russian separatist leaders.

President Barack Obama on Thursday hailed Congress for backing his plan to arm moderate Syrian rebels and France for signing off on air strikes in Iraq, victories for his campaign to destroy the Islamic State group.

U.S. warplanes meanwhile hit an Islamic State group training camp in Iraq in their first strike not directly supporting Iraqi or Kurdish forces as Washington cranked up  pressure on the Sunni extremist group.

For the first time since President Barack Obama took office, more Americans disapprove than approve his handling of terror threats, The New York Times reported Thursday, citing a new poll.

The slide in the president's approval ratings on terrorism comes as the White House ramps up its fight against the Islamic State group that recently beheaded three Westerners, including two U.S. journalists.  

Ukrainian leader Petro Poroshenko will cast Russia as a global menace Thursday when he meets U.S. President Barack Obama in the hope of winning a "special status" guaranteeing his troubled nation's security.

The pro-Western president's first tour of the White House since his May election comes two days after Ukraine took its first firm step out of Russia's orbit by ratifying a landmark political and economic partnership pact with the 28-nation EU bloc.

President Barack Obama insisted Wednesday that U.S. troops have no combat mission in Iraq, after his top general suggested some U.S. advisers could join Iraqi forces to fight the Islamic State group.

"The American forces that have been deployed to Iraq do not and will not have a combat mission," Obama told American troops at the headquarters of U.S. Central Command in Florida.

Iranian President Hassan Rouhani will address the U.N. General Assembly in New York next week but is not scheduled to meet Barack Obama, a government spokesman said on Wednesday.

Rouhani's first major foreign visit as president was to last year's General Assembly, where he held a historic telephone call with Obama on the sidelines, the highest level contact between the two countries since Iran's 1979 Islamic revolution.

The office of Iran's supreme leader published a series of graphics on Wednesday highlighting how little he believes the country has gained from dialogue with Washington as nuclear talks resume.

The top U.S. Republican said Tuesday he backed President Barack Obama's "sound" plan to arm and train vetted Syrian rebels for battling extremists and called on Congress to authorize the action.

Lawmakers began a marathon debate on the strategy, with many seeking a united front for the commander-in-chief's opening salvo against jihadists in Syria but adamant that Congress firm up its role in whether to authorize broader military action.