Israel is willing to resort to military action to ensure Iran never acquires nuclear weapons, the intelligence minister said on Thursday in Japan where he is seeking backing for U.S. President Donald Trump's tougher line on Tehran.

Trump said on October 13 he would not certify Iran is complying with an agreement on curtailing its nuclear program, signed by his predecessor, Barack Obama, opening a 60-day window for Congress to act to reimpose sanctions.

>> In Netanyahu's latest rant, Iran's meddling in Syria overcame the nuclear threat | Analysis <<

Open gallery view Minister of Transportation and Intelligence Israel Katz at a weekly government meeting on May 17, 2017. Credit: Marc Israel Sellem

"If international efforts led these days by U.S. President Trump don't help stop Iran attaining nuclear capabilities, Israel will act militarily by itself," Intelligence Minister Israel Katz said in an interview in Tokyo. "There are changes that can be made (to the agreement) to ensure that they will never have the ability to have a nuclear weapon."

Israel has taken unilateral action in the past without the consent of its major ally, the United States, including air strikes on a suspected nuclear reactor in Syria in 2007 and in Iraq in 1981. A strike against Iran, however, would be a risky venture with the potential to provoke a counter strike and roil financial markets.

An Israeli threat of military strikes could, nonetheless, galvanize support in the United States for toughening up the nuclear agreement but it could also backfire by encouraging hardliners in Iran and widening a rift between Washington and European allies.

So far, none of the other signatories to the deal - Britain, France, Germany, Russia, China, Iran and the European Union - has cited serious concerns, leaving the United States isolated.

Japan relies on the U.S. military to help defend it against threats from North Korea and elsewhere. Tokyo's diplomatic strategy in the Middle East, where it buys almost all its oil, is to maintain friendly relations with all countries, including Iran.

"I asked the Japanese government to support steps led by President Trump to change the nuclear agreement," said Katz, who is a member of Prime Minister Benjamin Netanyahu's right-wing Likud party. "The question of whether Japanese companies will begin to work in Iran or not is a very important question."

Katz's visit to Tokyo comes ahead of a planned trip by Trump from November 5 for a summit with Prime Minister Shinzo Abe. Officials at Japan's Ministry of Foreign Affairs were not immediately available to comment.

Israel, Katz said, wants the nuclear agreement to be revised to remove an expiration date, and to impose tighter conditions to stop Tehran from developing new centrifuges used to make weapons-grade nuclear material.

He also urged sanctions to stop Iran from establishing Syria as a military base to launch attacks on Israel and action to put a halt to Tehran's development of ballistic missiles.

"We will not allow Iran to transform Syria into forward base sea harbours, air bases and Shia militias," he said. "We will act together with the United States and other countries in the world until they stop the ballistic missiles that threaten Israel."

The U.S. House of Representatives on Wednesday backed new sanctions on Lebanon's Iran-backed Hezbollah militia.