Netanyahu had travelled to Washington for his seventh meeting with Trump since the US president returned to power, and had sought to push for a harder line in nuclear talks with Iran.

"The president believes that the Iranians have already learned who they are dealing with," Netanyahu said in Washington before departing for Israel, according to a video statement from his office.

"He believes that the conditions he is creating, combined with the fact that they surely understand they made a mistake last time when they didn't reach an agreement, may create the conditions for achieving a good deal," he added.

"I will not hide from you that I expressed general skepticism regarding the quality of any agreement with Iran."

Any deal "must include the elements that are very important from our perspective", Netanyahu continued, listing Iran's ballistic missile programme and its support for militant groups such as the Palestinian movement Hamas, Yemen's Houthi rebels and Hezbollah in Lebanon.

"It's not just the nuclear issue," he said.

On Wednesday, Trump had told Netanyahu at the White House that talks with Iran must continue, rebuffing the Israeli leader's push for a tougher stance.

Trump said his preference was that a deal be reached, but added: "If it cannot, we will just have to see what the outcome will be."

The US president has repeatedly hinted at potential US military action against Iran following its deadly crackdown on protests last month, even as Washington and Tehran restarted talks last week with a meeting in Oman.

The last round of talks between the two foes was cut short by Israel's 12-day war with Iran in June, which the US briefly joined with strikes on nuclear facilities.

So far, Iran has rejected expanding the new talks beyond the issue of its nuclear programme, though Washington also wants Tehran's ballistic missile programme and its support for regional militant groups on the table.