President Barack Obama has said the United States has done everything it can to convince Russia to change course in Ukraine, where the government is battling pro-Russian separatists.
Speaking at the White House on August 1, Obama said the United States is limited in what it can do to pressure Russia to withdraw support for Ukrainian rebels.
“Short of going to war, he said, there are going to be some constraints in terms of what we can do if President Putin and Russia are ignoring what should be their long-term interests."
Obama said sanctions have imposed sufficient costs on Russia and that should lead Putin to want to resolve the Ukraine crisis.
But he added: "Sometimes people don't always act rationally."
Earlier on August 1, the two leaders discussed the crisis in Ukraine during a telephone conversation.
The Kremlin quoted Putin as telling Obama that Western sanctions against his country are "counterproductive."
The Kremlin also said the two leaders agreed that the current standoff in Ukraine was "not in the interest of either country."
The White House said Obama told Putin of his "deep concerns" about Moscow's increased support for separatists in Ukraine.
It also said the two leaders agreed to keep open their channels of communication.
Obama also raised his concerns about what Washington says was a violation by Russia of a 1987 treaty designed to eliminate U.S. and Russian ground-launched missiles with intermediate ranges.
Russia has described the allegation as "unfounded."
Also on August 1, the Pentagon announced that the Obama administration has asked Congress for authority to spend $19 million next year to train and equip Ukrainian National Guard forces.
Pentagon spokesman Rear Admiral John Kirby said Russian troops have moved closer to the border with Ukraine and continue to build their military capabilities in the region.
He added that Moscow continues to maintain at least 10,000 troops near the Ukrainian border.
Earlier in the day, U.S. Vice President Joe Biden spoke with Ukrainian President Petro Poroshenko and told him the United States will provide $8 million in new assistance to bolster Ukraine's border security.
With reporting by AP, AFP, and Reuters