No meeting scheduled with Rouhani: Trump

US President Donald Trump on Monday said he has no meeting scheduled with his Iranian counterpart Hassan Rouhani on the sidelines of the UN General Assembly in New York later this month.

"I have no meeting scheduled (with Rouhani). I know they (Iranians) want to meet," Trump told reporters at the White House.

"I know they are not doing well as a country. Iran has got a lot of problems right now.. but two and half to three years ago they were causing a lot of trouble... and we'll see what happens," he said.

After coming to power, Trump had withdrawn from the Iranian nuclear deal and imposed stringent sanctions on Iran.

Trump said certain conditions had to be met for talks with the Iranians.

"The biggest thing you can talk about are the sanctions, and the sanctions are massive. There's never been sanctions put on a country like that. I think they have a tremendous future, but not the way they're behaving," he said.

Responding to a question, Trump said the evidence from the recent attack on the oil units in Saudi Arabia indicated foul play from Iran.

"It's looking that way. We are having some very strong studies done, but it's certainly looking that way at this moment. And we'll let you know. As soon as we find out definitively, we'll let you know. But it does look that way," he said.

On Saturday, air attacks targeted Abqaiq, the site of the largest oil processing plant run by the Saudi state oil company, Aramco, and the Khurais oilfield.

Iran has denied involvement in the air attacks, which were claimed by Iran-aligned Houthi rebels in Yemen.

Secretary of State, Mike Pompeo and other US officials will be visiting Saudi Arabia to hold talks in the aftermath of the attacks.

Trump said: "We have a lot of options, but I'm not looking at options right now. We want to find definitively who did this. We're dealing with Saudi Arabia. We're dealing with the Crown Prince and so many other of your neighbours, and we're all talking about it together. We'll see what happens," he said.

Trump said he is against war. "Do I want war? I don't want war with anybody. I'm somebody that would like not to have war. We have the strongest military in the world. We've spent more than a trillion-and-a-half dollars in the last short period of time on our military. Nobody has even come close," he said.