Mr Obama took time out from a visit to Moscow to calm concerns over Iran
The US has "absolutely not" given Israel a green light to attack Iran over its nuclear programme, President Barack Obama has said.
His remarks followed weekend comments by Vice-President Joe Biden that the US would not stand in the way of Israel's response to Iran's nuclear ambitions.
Meanwhile, US military chief Adm Mike Mullen said Washington should keep military options on the table.
But he said he hoped dialogue with Tehran would prove productive.
Speaking to CNN while on a visit to Russia, President Obama said the US would to try to resolve the Iranian nuclear issue "in a peaceful way through diplomatic channels."
Vice-President Joe Biden had said in an interview with ABC TV on Sunday that "Israel can determine for itself... what's in their interest and what they decide to do relative to Iran and anyone else".
Asked whether the comment meant that Washington had given Israel the go-ahead for an attack, Mr Obama said: "Absolutely not."
However, he did defend his deputy, who was accused of being gaffe-prone by rivals during the 2008 presidential election campaign.
"I think Vice-President Biden stated a categorical fact which is we can't dictate to other countries what their security interests are," Mr Obama added.
He added that the US also reserved the right to take "whatever actions" were necessary to protect itself, without elaborating what those were.
At an event in Washington Adm Mullen, the chairman of the US Joint Chiefs of Staff, echoed the president's comments.
"There is a great deal that certainly depends on the dialogue and the engagement, and I think we need to do that with all options remaining on the table, including certainly military options," he said.
The US military chief said Tehran could have an atomic bomb within one to three years, which "would be potentially very destabilising" to the Middle East.
But he said the potential consequences of an attack on Iran were of great concern and weighed heavily against launching any strike.
"I worry a great deal about the response of a country that gets struck."