U.S. Republican Senator John McCain has said that the supply of defensive weapons from the United States to Ukraine is needed to stop the Russian aggression from getting further into Ukraine's east.

"Right now the weapons are a critical issue in preventing Vladimir Putin from further encroachment in eastern Ukraine," he said during a televised conference at the Ukraine Crisis Media Center at a briefing in Kyiv on Saturday.

According to him, Ukraine is now fighting with the 20th century weapons against the 21st century weapons.

The Republican senators will continue to urge the U.S. government to authorize the dispatch of defensive weapons to Ukraine, that can help Ukrainians defend their sovereign country, McCain said.

McCain recalled that the Senate was defending the need for providing defensive weapons Ukraine, but this decision was up to President Barack Obama's administration.

The U.S. has a tradition of helping the people who are fighting for freedom against the occupation of other countries, he said.

"Frankly it's shameful that our European friends wouldn't be of more assistance but more shameful that the United States won't lead," McCain said.

"Vladimir Putin I believe yesterday or the day before talked about Ukraine and Russia being one country. Is there any doubt about what his ambitions are? Is there any doubt what he's trying to achieve by force of arms that he could never achieve by free and open election and other democracy?" the senator said.