U.S. President Barack Obama earlier Tuesday rebuffed suggestions that Washington had given Israel a green light to attack Iran's nuclear facilities, in an interview with CNN.

Asked by CNN whether Washington had given Israel approval to strike Iran's nuclear facilities, Obama answered: "Absolutely not."

"We have said directly to the Israelis that it is important to try and resolve this in an international setting in a way that does not create major conflict in the Middle East," Obama said in reference to Iran's contentious nuclear program.

In the interview broadcast from Russia where he is on an official visit, Obama added, however: "We can't dictate to other countries what their security interests are.

"What is also true is, it is the policy of the United States to try to resolve the issue of Iran's nuclear capabilities," Obama said.

This would be achieved "through diplomatic channels," he added.

Sources close to Prime Minister Benjamin Netanyahu told The Washington Times that the premier is hesitant to request formal U.S. approval to launch military operations against Iran for fear that Washington would turn him down, according to a report which appeared in Tuesday editions.

The sources said the Israeli leader feels there is no point in seeking American acquiescence at this stage givenObama's stated intention to pursue a policy of diplomatic engagement with the Tehran regime, The Washington Times reported.

"There was a decision not to press [for U.S. approval of a strike] because it was probably inadequate for the engagement policy and what we know about Obama's approach to Iran," a senior Israeli official told The Washington Times.

Discussion over authorization for such a strike arose after Vice President Joe Biden told ABC news earlier this week that the U.S. would not stand in the way of an Israeli attack on Iran.

"Israel can determine for itself - it's a sovereign nation - what's in their interest and what they decide to do relative to Iran and anyone else," Biden said.

U.S.: Iran strike should be avoided if possible

The chairman of the U.S. Joint Chiefs of Staff said on Tuesday that a preemptive military strike against Iran should be avoided "if possible," but emphasized that all options are still on the table.

"I worry about a nuclear arms race in the Middle East region; I don't think any one of us can afford it," said Admiral Michael Mullen, during a conference at the Center for Strategic and International Studies. "I don't see a lot of space between where Iran is headed and the potential of where that development might lead. All options are certainly on a table, including certainly military options."

My concern is that the clock continues ticking," Mullen said. "I believe that Iran is very much focused on getting that capability. This a very narrow space we have towards that objective."

Nevertheless, Mullen added, a preemptive strike is "really not a place we should go if possible."

Israel's vulnerability to the Iranian threat is of ultimate concern to the United States, Mullen said. "The Israelis see that Iran achieving a nuclear capability as an existential threat. What's very important is to understand the word existential," he said.

"Israel is a sovereign country, but it's an essential part of this discussion," Mullen added. "Our political leadership is committed to the dialogue, and I'm hopeful that dialogue is productive - I'm really worried if it's not."

Obama: Russia must help end Iran threat

Obama, on a visit to Moscow on Tuesday, called for the United States and Russia to overcome Cold War mistrust and forge a true global partnership, saying that the U.S. wouldn't need to deploy a missile defense system in Europe, a move Russia opposes, if Russia helped to bring the Iranian nuclear threat to an end.

"If the threat from Iran's nuclear and ballistic missile program is eliminated, the driving force for missile defense in Europe will be eliminated," Obama said in remarks prepared for delivery to graduates from Moscow's New Economic School.

"America wants a strong, peaceful and prosperous Russia," Obama said. "On the fundamental issues that will shape this century, Americans and Russians share common interests that form a basis for cooperation," the U.S. President went on to say.

Obama also laid out a vision for the graduates of the sort of world he believed they should pursue.

"The future does not belong to those who gather armies on a field of battle or bury missiles in the ground," he told his audience. "The future belongs to young people with the education and imagination to create."

But he also told the Russian students that success in the 21st century depended on economies that functioned within the rule of law.

"People everywhere should have the right to do business or get an education without paying a bribe," he said, in an apparent reference to the corruption which even President Medvedev says blights Russian society.

Obama was careful in his remarks not to criticize the Kremlin leadership directly and he repeatedly said that the United States did not seek to impose any system of government on another country.

But his message that "governments which serve their own people survive and thrive; governments which serve only their own power do not" is likely to resonate with Russia's embattled pro-Western opposition, which criticizes the Kremlin for suppressing democracy.