Donald Trump talks tough, says Iran must stop 'supporting terrorists'

U.S. President Donald Trump said on Monday that Iran must immediately stop its financial and military support for "terrorists and militas" and he reiterated that it never be permitted to possess atomic arms.

"Most importantly, the United States and Israel can declare with one voice that Iran must never be allowed to possess a nuclear weapon - never, ever - and must cease its deadly funding, training and equipping of terrorists and militias, and it must cease immediately," Trump said in public remarks at a meeting in Jerusalem with Israeli President Reuven Rivlin.

The United States brands Iran a "state sponsor of terrorism". It says Tehran's support for Syrian President Bashar al-Assad in Syria's civil war, Houthi rebels in Yemen's civil war and the Hezbollah Shi'ite political party and militia in Lebanon have helped destabilise the Middle East.

Trump flew to Israel from Riyadh earlier in the day, on the second leg of his first overseas trip since entering office in January.

In his speech at Rivlin's official residence, Trump said he was deeply encouraged by his conversations with Muslim world leaders in Saudi Arabia.

"Many expressed their resolve to help end terrorism and the spread of radicalisation. Many Muslim nations have already taken steps to begin following through on this commitment," he said.

"There is a growing realisation among your Arab neighbours that they have common cause with you in the threat posed by Iran," Trump told Rivlin.