Washington (AFP) - President Barack Obama on Thursday vowed to continue hammering Islamic State targets in Iraq and Syria, but acknowledged that pressure on the jihadists was prompting them to lash out beyond their self-proclaimed caliphate.
Speaking after meeting security and military officials in the Pentagon, Obama also blasted President Vladimir Putin's policy in Syria, saying he doubted the Russian leader could be trusted to cooperate on helping end the country's bloody civil war.
Obama pledged the IS group would "inevitably" be crushed and said the US-led coalition would continue to aggressively target the jihadists "across every front."
But "the decline of ISIL in Syria and Iraq appears to be causing it to shift to tactics that we've seen before -- an even greater emphasis on encouraging high-profile terrorist attacks, including in the United States," Obama warned, using an acronym for the IS group.
Even as coalition planes target the IS group in Iraq and Syria, the Russians have simultaneously been bombing in Syria to support President Bashar al-Assad.
While Moscow has sometimes struck IS targets, many of its strikes have been against anti-Assad rebels.
Multiple rounds of international negotiations to end the war, which erupted in 2011 after the Assad regime unleashed a brutal crackdown against a pro-democracy revolt, have so far failed.
Obama said the United States was prepared to work with Russia to try to reduce the violence in Syria and boost the fight against the IS group and Al-Qaeda.
"But Russia has failed to take the necessary steps. Given the deteriorating situation, it is time for Russia to show it is serious about pursuing these objectives," Obama said, warning he was not confident he could trust Putin.
"We go into this without any blinders on," Obama said.
"We're going to test and see if we can get something that sticks. And if not, then Russia will have shown itself very clearly to be an irresponsible actor around the world stage that is supporting a murderous regime."
Obama's visit to the Pentagon, possibly the last of his eight-year presidency, came as the US-led effort to defeat the IS group enters its third year.
The jihadists swept across vast parts of northern Syria and Iraq in 2014, leaving a trail of human butchery and horrific destruction in their wake.
Since then, the coalition has conducted daily plane and drone strikes -- more than 14,000 so far -- and worked with local forces on the ground to gradually reclaim the seized territory.
Despite the massive effort, the jihadists still hold Mosul -- Iraq's second-largest city -- and the Syrian city of Raqa.