Vladimir Putin's Russia has slid back toward the suspicions and mistrust of the Cold War contest with the United States, U.S. President Barack Obama said Friday, adding that it is appropriate to "reassess" a relationship that has been damaged most recently by the case of National Security Agency leaker Edward Snowden.

In a White House news conference, Obama defended his decision to cancel a planned summit in Moscow with Putin next month. Obama blamed Putin, who reassumed the presidency last year, for souring what Obama called a productive partnership forged with former leader Dmitry Medvedev.

"I think we saw more rhetoric on the Russian side that was anti-American, that played into some of the old stereotypes about the Cold War contest between the United States and Russia," Obama said of the ex-KGB officer's return to power last year. "I've encouraged Mr. Putin to think forward as opposed to backwards on those issues, with mixed success."