Leading American senators have called for the US to send weapons to help Ukraine fight what they say is "a Russian invasion".

Robert Menendez, head of the Senate Foreign Relations Committee, said Russia's President Vladimir Putin must face a cost for his "aggression".

Senator John McCain said: "This is not an incursion. This is an invasion."

Earlier, Mr Putin called for talks to discuss the matter of "statehood" for eastern Ukraine.

Meanwhile, a meeting of the so-called Contact Group on Ukraine is expected to start later on Monday in Minsk, Belarus.

Representatives of Ukraine, Russia and the Organization for Security and Co-operation in Europe will attend the talks. The participation of pro-Russian rebels from eastern Ukraine remains unclear.

Last week's first direct talks between Mr Putin and Ukrainian President Petro Poroshenko in Minsk did not lead to any major breakthrough.

The conflict in eastern Ukraine erupted in April following Russia's annexation of Ukraine's southern Crimea peninsula a month before. Some 2,600 people have died since April.

The pro-Russian separatists have been gaining ground on Ukrainian forces in recent days, in both the Luhansk and Donetsk regions, and further south around the port of Mariupol.

Speaking on CNN, Mr Menendez, a Democrat, said: "We should provide the Ukrainians with the type of defensive weapons that will impose a cost upon Putin for further aggression.

"This is no longer the question of some rebel separatists, this is a direct invasion by Russia. We must recognise it as that."

He said the issue "may very well be on the table right now" for President Barack Obama.

Senator McCain told CBS's Face the Nation that Mr Putin was "an old KGB colonel that wants to restore the Russian empire".

Mr McCain called for "strong sanctions", before adding that Ukraine must be supplied with weapons: "Give them the weapons they need. Give them the wherewithal they need. Give them the ability to fight."

Representative Mike Rogers, chairman of the House Intelligence Committee, told Fox News: "If we don't provide 'small and effective' now, you're going to get very big and very ugly later."

(BBC)