U.S. Secretary of State Hillary Clinton said Thursday that Ukraine's landmark naval-base-for-gas deal with Russia was part of a delicate foreign policy "balancing act" for President Viktor Yanukovych.

"
Ukraine is trying to have a balanced approach to its foreign policy," Clinton told reporters in Estonia ahead of talks with her North Atlantic Treaty Organization counterparts.

Yanukovych has told U.S. President Barack Obama "that he very much wants to improve and deepen relations with the
United States , but at the same time he has made it clear he is going to continue to work with Russia ," she said.

"I think given
Ukraine 's history and Ukraine 's geographic position, that balancing act is a hard one, but it makes sense to us. That's what he's trying to do and, to keep a foot, if you will, in both sides of his country."

Russia and Ukraine Wednesday announced a landmark deal to extend the lease of a strategic Russian naval base in Crimea by 25 years in exchange for Kiev receiving a huge discount on natural gas imports.

The deal, announced after talks between Yanukovych and his Russian counterpart Dmitry Medvedev, is the most substantive result yet of warming in ties between Ukraine and Russia after Yanukovych's election in February.

The
U.S. has long supported the candidature of Ukraine to join NATO, which was pushed by Ukraine 's former pro-Western president Viktor Yushchenko.