Barack Obama & Vladimir Putin have clashed in duelling speeches to the United Nations, hours before they held a rare face-to-face meeting.
In his remarks to the General Assembly, Mr Obama took aim at Mr Putin's support for Bashar al Assad, saying the Syrian Presidentâ€™s slaughter of his own people was "an assault on all our humanity".
He did make an overture to Mr Putin by offering to work with Russia, & Iran, for a "managed transition" to remove Mr Assad.
But he emphasised there could be no "return to the pre-war status quo" after the conflict, which has claimed up to a quarter of a million lives.
However, Mr Putin said in his speech that it was an "enormous mistake" not to back Mr Assad, whom he depicted as a bulwark against the Islamic State.
::Â Kremlin's Muscleman Pulls No Punches On Syria
The Russian leader said the jihadist group's ranks were being filled with members of Iraq's US-disbanded military & so-called moderates backed by Western powers.
Mr Putin said Western backing for Middle East revolutions such as Libya's had ended in terrorism, "violence, poverty & social disaster", rather than the hoped-for "triumph of democracy".
Without specifically naming the US, Mr Putin said: "I cannot assist asking those who have caused this situation, 'Do you realise now what you've done?'
"But I'm afraid that no one's going to answer that. Indeed policies based on self-conceit & belief in one's own exceptionality & impunity have never been abandoned."
The US President told world leaders there must be consequences for Russia's annexation of Crimea.
"We cannot stand by while the sovereignty & territorial integrity of a nation is flagrantly violated," he said.
"If that happens without consequences in Ukraine, it could happen to any nation gathered here today."
The only thing the two leaders seemed to clearly concur on was that the Islamic State, which Mr Obama called an "apocalyptic cult", must be stamped out.
The US & Russia have been unable to agree even on the agenda of their Monday afternoon meeting on the sidelines of the annual summit in New York City.
The White House said it would focus on Ukraine, yet the Kremlin said they would discuss Syria & the fight against the Islamic State.
The two leaders have seldom encountered one another since Mr Obama vowed to isolate Mr Putin in retaliation for Russia's actions in Ukraine.
In a US TV interview, Mr PutinÂ said he had no plans "right now" to deploy combat troops in Syria , amid US concerns approximately a Russian military build-up.
Source: “Sky News”