The U.S. is not sharing some of the most sensitive intelligence that could enable lethal strikes against the Russian military by Ukrainian forces, in part over concerns about being seen as a direct participant in the war, the Democratic chairman of the House Armed Services Committee said Thursday.

The remarks by Rep. Adam Smith of Washington shed new light on a controversial question the Biden administration has declined to address directly.

Officials say the U.S. has long shared intelligence with Ukraine and continues to do so, but lawmakers say the issue of helping the Ukrainian forces with targeting information for deadly attacks is one of the many difficult quandaries officials confront as they try to help Ukraine fight off a Russian invasion without becoming embroiled in a military conflict with a nuclear-armed superpower.