The Illinois senator's comments come a day after US media projected that Obama had enough delegates to win the Democratic nomination and face John McCain, the presumptive Republican candidate, in the November election.
Obama also had harsh words for Iran, vowing to work to "eliminate" the threat it posed to security in the Middle East and around the globe.
"There's no greater threat to Israel or to the peace and stability of the region than Iran," he told the Aipac assembly.
|Obama said an "undivided Jerusalem should |
remain the capital of Israel" [AFP]
Calling for "aggressive, principled diplomacy" with Tehran, he also warned he would never take the military option off the table in guaranteeing US and Israeli security.
Iranians responded cautiously, but optimisticly, with officials expressing hope he can bring about change in Iran-US relations.
Hamidreza Hajibabaee, member of Iranian parliament, said: "We hope that Obama turns his words into actions, helps the Islamic Republic of Iran believe that the US has given up enmity and paves the way for fair negotiations."