Talks between Iran and the United States would be possible if they are based on an agenda that could lead to tangible results, but Washington is not seeking dialogue, Iran's Foreign Ministry spokesman Seyyed Abbas Mousavi said Monday.

U.S. President Donald Trump has said he's willing to hold talks with the Islamic Republic.

"Dialogue and negotiation can be held when we have a certain agenda in place and when we could get some tangible and practical results out of it," Mousavi said in a news conference broadcast live on Press TV.

He added: "They are not for talks. They are not seeking dialogue."

Tensions have been running high between Iran and the United States since U.S. withdrew from a landmark 2015 nuclear deal last year and reimposed biting sanctions against Iran as part of a "maximum pressure" campaign.

Iran's President Hassan Rouhani said last week Iran is ready for "just" negotiations but not if they mean surrender.

"As long as I have the responsibility for the executive duties of the country, we are completely ready for just, legal and honest negotiations to solve the problems," Rouhani said, according to his official website.

"But at the same time we are not ready to sit at the table of surrender under the name of negotiations," Rouhani said.

The head of Iran's Atomic Energy Organization, Ali Akbar Salehi, said Sunday that Iran will restart activities at the Arak heavy water nuclear reactor, according to ISNA news agency.

Heavy water can be employed in reactors to produce plutonium, a fuel used in nuclear warheads, ISNA said.

Parties to Iran's 2015 nuclear deal met in Vienna on Sunday for emergency talks called in response to an escalation in tensions between Iran and the West that included confrontations at sea and Tehran's breaches of the accord. China, Britain, France, Germany, Russia and Iran have been trying to salvage the pact.

During the meeting, China called on all parties to maintain calm and restraint, ease the current situation, and take their respective responsibilities, Hua Chunying, a spokeswoman for the Chinese Foreign Ministry said Monday.

Unilateral sanctions and long-arm jurisdiction by the U.S. are the root of the tension and China hopes all parties exercise restraint and play a positive role for the peace in the Middle East, the spokeswoman said.

(With input from Reuters)