U.S. Sen. John McCain has said during a visit to Ukraine that it is shameful that Washington's European allies have not done more to assist Ukrainian forces in their quest to defeat Russian-backed separatists in the east.

McCain was part of a delegation of U.S. senators that met Saturday with senior Ukrainian officials, including President Petro Poroshenko, after visiting troops and volunteers working on the front line.

The U.S. Senate this week approved a bill that includes provisions to supply Ukraine with $300 million worth of defensive military equipment. Approval from Congress and the White House is still pending.

European countries have favored a diplomatic settlement as a way out of the conflict.

Russia condemns U.S. military aid to Ukraine and says it will foment instability.