Carolyn Kaster, AP
In a Friday, Jan. 30, 2015 file photo, President Barack Obama speaks in the East Room of the White House in Washington.

WASHINGTON — President Barack Obama is reconsidering sending lethal assistance to Ukraine, a senior administration official said Monday, but continues to have concerns about taking that step.

This official, who requested anonymity to speak because the person wasn't authorized to talk publicly about internal deliberations, said the president is worried about starting a proxy war with Russia and that he's also concerned about the Ukrainian military's capacity for effectively using high-powered weaponry.

The official said Obama worries that no amount of arming the Ukrainians would put them on par with Russia's military prowess. The U.S. accuses Russia of supplying the pro-Kremlin separatists that are stirring instability in eastern Ukraine.

The official said the recent escalation of violence in eastern Ukraine has caused the White House to take a fresh look at lethal aid options. The U.S. currently supplies the Ukrainian military only with non-lethal assistance, such as gas masks and radar technology to detect incoming fire.

A decision on escalating aid is not imminent, the official cautioned, and this person said that Obama would want to first discuss the issue with European leaders, including German Chancellor Angela Merkel. She is scheduled to visit Washington next week. Secretary of State John Kerry is scheduled to travel to Kiev Thursday to meet with Ukrainian officials.

The New York Times first reported the new Obama administration deliberations.

Bernadette Meehan, spokeswoman for the White House National Security Council, said the White House is "constantly assessing our policies in Ukraine."

"Although our focus remains on pursuing a solution through diplomatic means," she said, "we are always evaluating other options that will help create space for a negotiated solution to the crisis."