Washington (AFP) - US presidential hopeful Donald Trump declared Monday that his first foreign policy priority would be to dismantle the Iran nuclear deal and what he said was Tehran's global terror network.

"My number one priority is to dismantle the disastrous deal with Iran," the Republican frontrunner told the conference of the US pro-Israel lobby AIPAC in Washington.

"I have been in business a long time. I know deal making. And let me tell you, this deal is catastrophic. For America, for Israel and for the whole of the Middle East."

Trump -- unusually, speaking from a teleprompter -- did not receive as warm a reception at the AIPAC event as he does in his bombastic campaign rallies, but the crowd warmed to his attacks on Iran and US President Barack Obama.

"With President Obama in his final year -- yeah! -- he may be the worst thing to ever happen to Israel, believe me. Believe me," he said to applause.

"We will totally dismantle Iran's global terror network which is big and powerful but not powerful like us," he vowed, accusing the current White House of pressuring US allies while rewarding enemies like Iran.