U.S. Democratic and Republican lawmakers on Sunday urged Washington to arm the Ukrainian government, saying it needed help to repel what they called Russia's invasion of the country.

Sen. Robert Menendez, who heads the Senate Foreign Relations Committee, told CNN the United States, European Union and NATO should work together to arm Kiev, which has been fighting Russian-backed rebels in eastern Ukraine for months.

"We ... should be providing the Ukrainians with the types of defensive weapons that will impose a cost upon (Russian President Vladimir) Putin for further aggression," the New Jersey Democrat told the "State of the Union" program from Kiev.