The UN on Monday urged the U.S. and Iran to de-escalate tensions as the rivals continue to engage in tit-for-tat recriminations.

Axar.az reports citing Turkish media.

Spokesman Stephane Dujarric told reporters at the UN's New York headquarters that the international body is "concerned about the rising rhetoric," further asking all parties concerned to take a calmer approach in a complex region.

"It is a very volatile region," Dujarric said. "Any developments, whether they are actions on the ground, whether they are rhetoric, they can always be misinterpreted and can only heighten the risk of a volatile region becoming more volatile."

Dujarric's appeal comes as U.S. President Donald Trump denied reports that the U.S. is seeking to establish negotiations with Iran.

"Iran will call us if and when they are ever ready," Trump said on Twitter. "In the meantime, their economy continues to collapse - very sad for the Iranian people!"

The president's remarks strike a much different tone than comments he delivered Sunday, warning Iran that if it pursues conflict with the U.S., "that will be the official end of Iran!"

"Never threaten the United States again!" he said, without specifying which threat he was referring to, though a rocket had landed in Baghdad's Green Zone -- where the U.S. embassy is located -- earlier in the day.

Iranian Foreign Minister Javad Zarif responded, saying Trump "hopes to achieve what Alexander, Genghis & other aggressors failed to do," referring to some of history's most prolific conquerors.

"Iranians have stood tall for millennia while aggressors all gone," Zarif tweeted. "#NeverThreatenAnIranian. Try respect—it works!"

Iran's UN mission followed up in a letter to the Security Council and Secretary General Antonio Guterres saying that while Tehran does not seek war, if it is imposed "on us, Iran will vigorously exercise its inherent right to self-defense in order to defend its nation and to secure its interests".

Majid Takht-Ravanchi, Iran's UN ambassador, further urged the creation of a collective dialogue forum between Persian Gulf states.

Tensions have risen since Trump decided to unilaterally withdraw the U.S. from an international pact world powers struck with Iran to curb its nuclear program.

At the time, European leaders urged Trump not to do so, warning tensions would escalate in the region.

The Trump administration went on to pursue a number of efforts meant to scuttle the agreement, including the reimposition of U.S. sanctions on Iranian oil, which went into full effect earlier in May.

Iran reportedly said earlier Monday that it has increased its uranium enrichment fourfold, which would likely breach the stockpile limits the 2015 agreement set.