WASHINGTON—The U.S. government is considering providing Javelin antitank missiles, small arms and ammunition to Ukraine, part of an effort to try to deter further aggression by Russia-backed rebels there, according to U.S. officials.

The Pentagon has long supported providing some lethal aid, but until recently the White House has signaled little interest in such a move to avoid escalating the confrontation with Russian President Vladimir Putin.

However, amid a surge of new fighting in eastern Ukraine, the White House and military leaders have begun taking another look at providing lethal assistance such as the antitank missiles. An administration official said Susan Rice, the White House national-security adviser, has reopened the discussion, though officials cautioned that no decision has been made.

Similar discussions have taken place throughout the past several months.

The U.S. has been providing nonlethal military aid, including protective vests, night-vision goggles and counter-mortar radar systems, to Ukraine in recent months. But so far, it hasn’t provided arms or ammunition.