Former US secretary of state Hillary Clinton has pledged to confront Russia at the head of the NATO coalition, but her one remaining challenger says European nations should carry more of their own defense burden, Senator Bernie Sanders said during the ninth Democratic presidential debate in Brooklyn, New York.

WASHINGTON (Sputnik) – NATO suspended cooperation with Moscow in April 2014 in protest against Ukraine’s former republic of Crimea’s reunification with Russia after a referendum. NATO has accused Moscow of being involved in the internal conflict in Ukraine.

Russia has repeatedly dismissed the allegations of meddling in Ukrainian affairs and stressed that NATO's military expansion and increased presence near Russian borders undermines regional security.

"I would not be embarrassed as president of the United States to say to our European allies, you know what, the United States of America cannot just support your economies," Sanders said. "You [have] got to put up your own fair share of the defense burden. Nothing wrong with that."

Clinton, however, said the United States had to retain its leadership role in NATO as she accused Russia of being aggressive and intimidating towards the three Baltic republics of Latvia, Lithuania and Estonia.

"With Russia being more aggressive, making all kinds of intimidating moves toward the Baltic countries, we've seen what they've done in eastern Ukraine, we know how they want to rewrite the map of Europe…Think of how much it would cost if Russia's aggression were not deterred because NATO was there on the front lines making it clear they could not move forward."