Iran says US President Donald Trump's accusations of Iranian support for terrorism are "unbelievable" and "unacceptable", made in a country which is known for being "a haven and a promoter of violence and terrorism".

Trump's claims were made during his recent visit to Saudi Arabia where he accused Iran of destabilizing the Middle East and supporting terrorist groups, meaning Hezbollah which is fighting Takfiri terrorists backed by Riyadh in Syria.

"These misplaced, misguided and irrelevant positions by certain countries are not a new debate. They are part of a blame-game and the remarks are unbelievable and unacceptable," Foreign Ministry spokesman Bahram Qassemi said on Monday.

"Trump's visit to a country which is a haven and a promoter of violence and terrorism makes his allegations invalid. He has to answer how Iran which was holding glorious elections can be a promoter of terrorism."

The US president's visit to Saudi Arabia came during hotly-contested elections which gave President Hassan Rouhani another four-year term. Trump traveled to the kingdom on his first foreign visit during which he signed a $110-billion arms deal.

Trump named Iran as the target of the deal and urged cooperative measures between the signatories and other Arab countries against what it called Iran's unfavorable regional role.

“He travels to a country, which has been convicted in American courts,” Qassemi said, referring to criminal conviction of Saudi agents at US tribunals for their role in the September 11, 2001 terror attacks.

The Iranian spokesman said Saudi Arabia is “a country, whose positions on extremism and terrorism over the past decades are clear.”

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Syria deescalation talks

Qassemi said Iran, Russia and Turkey are seriously continuing efforts as part of the Astana talks to maintain a ceasefire in Syria.

The talks have been focusing on reinforcing the standing truce, which has resulted in the creation of four deescalation zones in Syria.

Qassemi said once an agreement is reached, the guarantors are needed to dispatch troops to the zones to monitor the ceasefire.

"The Astana debate is constantly underway and talks continue. There are negotiations among the three countries on reducing tensions and if the necessary conditions are met, the three countries are required to send troops in order to supervise the ceasefire," he said.

"We are ready to grant this if the necessary understanding is reached," Qassemi added.

Riyadh statement

Qassemi also addressed the issue of the Arab-American summit at the King Abdulaziz Conference Center, which took place in Riyadh on May 21.

Riyadh issued a statement at the conclusion of the summit, also attended by Trump, which included some anti-Iran articles.

One article featured the Saudi-American agreement “on the need to stop Iranian intervention in other countries’ internal affairs,” while another called Iran’s ballistic missile program “dangerous.”

Qassemi said the statement was a “unilateral” one, issued either without the other Arab attendees’ knowledge or contrary to their respective positions.

“The meeting was met with some setbacks and frustration, which will become clear in the future,” he added.

“Our policy concerning the neighboring countries is clear. We have always tried to speak with them with the language of friendship and amity and to boost our commonalities…,” Qassemi said.

“We do not dictate to others what they should do, but warned in advance of the meeting about the Zionist plot aimed at creating schism in the Muslim world,” the official concluded.

Iran missile work to continue as before

Concerning the current anti-Iran pushes within the US political circles, the spokesman said Tehran would only react to those measures, which receive the US administration’s signature.

The congressional campaigns as well as two rounds of sanctions ratified since Trump’s January inauguration have targeted Iran’s missile program.

Qassemi reiterated that the missile work does not violate any UN Security Council resolution -- as the projectiles are not capable of carrying nuclear warheads -- and is completely of defensive and deterrent nature.

“The [missile] policy is not going to undergo any changes,” he asserted.