Comments by US President Barack Obama and Vice President Joe Biden about a possible Israeli attack on Iran's nuclear facilities were directed at Iran and meant to "distinguish" the US from Israel, national security adviser Uzi Arad said Wednesday. Arad also told The Associated Press that US leaders were signaling to Iran that Washington is still interested in diplomatic engagement. Speaking to ABC-TV on Sunday, Biden appeared to depart from his previous comment that an Israeli attack on Iran would be ill-advised, saying: "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." A day later during a visit to Moscow, Obama was asked by CNN if Biden's comment's represented the US giving Israel a "green light" to attack, to which he replied, "Absolutely not." The next day, the chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, warned that a military strike to thwart Iran's nuclear weapons capability could have grave and unpredictable consequences. Iran has denied trying to build nuclear bombs. Arad said the back-and-forth was an American message to Iran, rather than Israel, noting that Biden also said in the interview, "If the Iranians respond to the offer of engagement, we will engage." "My understanding of what Biden said is that the second part is the interesting part - not that Israel is sovereign to act, but that he said the United States acts differently. Essentially, he distinguished himself" from Israel, Arad said. "What was important for him was to transmit to the Iranians that we, the United States, are different." Arad said Obama's quick rebuttal was meant to clarify that the United States was still interested in engagement - despite prospects for dialogue being rattled by Iran's heavy crackdown on protesters in the country's disputed presidential election - and was not suggesting that his administration would not stand in the way of an Israeli strike. "The president felt the need to correct the impression that Biden's comments made," he added. Arad, one of Prime Minister Binyamin Netanyahu's top aides, said Israeli officials have often discussed the Iran issue in Washington. Arad insisted that Israel's right to decide its own self defense is a right that "the United States cannot take away from Israel."