The official said Obama is specifically concerned about the besieged Ukrainian military's capacity for using high-powered, American-supplied weaponry. The president has also argued that no amount of arming the Ukrainians would put them on par with Russia's military prowess.
The US accuses Russia of supplying the pro-Kremlin separatists that are stirring instability in eastern Ukraine.
The US has limited its supplies to the Ukrainian military to non-lethal aid, such as gas masks and radar technology to detect incoming fire.
While the White House has weighed this option previously, Obama has stuck with his opposition to lethal aid. However, the official said an uptick in violence in eastern Ukraine in recent weeks has spurred Obama to take a fresh look at supplying Ukraine with lethal aid, along with other options for calming tensions.
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A US military official said defensive lethal aid could include anti-tank missiles, such as the Javelin weapon system, along with armored vehicles. Other options could involve foreign military sales, training or other aid. The US and Europe could also ratchet up economic sanctions against Russia.
A decision on escalating aid is not imminent, the administration official cautioned, adding that Obama would want to first discuss the issue with European leaders, including German Chancellor Angela Merkel, who is due to visit Washington next week.