Iran's Khamenei rejects talks with United States.

A new development in relations between Tehran and Washington.

Iran's Supreme Leader Ayatollah Ali Khamenei said on Tuesday that Iran will never hold one-to-one talks with the United States.

(SOUNDBITE) (Farsi) IRANIAN SUPREME LEADER, AYATOLLAH ALI KHAMENEI, SAYING:

"If the U.S. took back its words, if they repent and return to the agreement they breached, if they became a member country of the contract parties, then they can participate in the company of countries negotiating with Iran. Without doing so no negotiation will take place in no level between the authorities of the Islamic Republic of Iran and Americans. Neither in New York, nor anywhere else."

But, he said, Iran could engage in multi-lateral discussions if the U.S. returns to the 2015 deal on Iran's nuclear programme.

Under that deal, sanctions from six world powers were lifted in return for Iran curbing its nuclear activities.

But Trump has stepped up sanctions since withdrawing from the nuclear pact last year.

Tensions between Tehran and Washington have risen once again after an attack at the weekend on major oil sites in Saudi Arabia.

It sent oil prices soaring and raised fears of a new Middle East conflict.

On Monday, President Trump said it looked like Iran was behind the attacks, but said he didn't want to go to war.

And he also didn't rule out talks with Tehran.

(SOUNDBITE) (English) U.S. PRESIDENT DONALD TRUMP, SAYING:

"Well, I have no meeting scheduled. I know they want to meet. I know they're not doing well as a country. Iran has got a lot of problems right now. We'll see what happens, but we'll let you know definitively.

Trump has said he could meet Iranian President Hassan Rouhani, possibly at the U.N. General Assembly in New York later this month.