Qatar's foreign minister has held talks with his Iranian counterpart in recent days in Tehran aiming to defuse escalating tensions in the Gulf, a source told Al Jazeera.
The purpose of the visit was to open new avenues to resolve the growing crisis between Iran and the United States and ease the volatile situation, said the highly-placed source familiar with details of the trip.
"The Qatari Foreign Minister Sheikh Mohammed bin Abdulrahman Al Thani has visited Iran in the past few days and met Iranian Foreign Minister Mohammad Javad Zarif in Tehran," the source said.
The source did not say whether Sheikh Mohammed met Iranian President Hassan Rouhani but confirmed the US was aware of the visit in advance.
The source did not know whether the Qatari foreign minister was carrying a message from the US.
The US recently deployed an aircraft carrier attack group and B-52 bombers to the Gulf, citing "threats" from Iranian forces. Tehran has accused Washington of "psychological warfare".
Washington applied new sanctions on Iran after pulling out of the landmark nuclear deal involving Tehran and world powers, which curbed the Islamic Republic's atomic weapons programme in exchange for sanctions relief.
Iran quickly dubbed the US a "state sponsor of terrorism" and designated US Central Command and its forces a "terrorist group".
Iran announced on Wednesday that it officially stopped some commitments under the 2015 nuclear deal following an order from its National Security Council, ISNA news agency reported.
Last week, Iran notified China, France, Germany, Russia and the United Kingdom of its decision to halt some commitments under the nuclear deal, a year after the US unilaterally withdrew from the accord and reimposed sanctions.
Under the nuclear deal, Tehran was allowed to produce low-enriched uranium with a 300kg limit, and produce heavy water with a stock capped around 130 tonnes.
Tehran could ship the excess amounts out of the country for storage or sale.
An official in the country's atomic energy body told ISNA that Iran now has no limit for the production of enriched uranium and heavy water.
Iran's initial moves do not appear to violate the nuclear deal yet. But Tehran has warned that unless the other signatories put in place measures to protect its economy from US sanctions within 60 days, it would start enriching uranium at a higher level.
In a speech broadcast on national television on May 8, Rouhani said Iran wanted to negotiate new terms with the remaining partners in the deal, but acknowledged the situation was dire.
"We felt that the nuclear deal needs a surgery and the painkiller pills of the last year have been ineffective," Rouhani said. "This surgery is for saving the deal, not destroying it."
The deal also caps the level of purity to which Iran can enrich uranium at 3.67 percent, far below the 90 percent of weapons-grade uranium. It is also well below the 20 percent level to which Iran enriched uranium before the deal.
Iranian Supreme Leader Ayatollah Ali Khamenei said on Tuesday there will not be a war with the US despite mounting tensions. Khamenei also said Tehran would not negotiate with the US on another nuclear deal.
On Tuesday, Iranian officials accused "hardliners" in the US and elsewhere of attempting to orchestrate an incident that would ratchet up tensions with Tehran.
Four ships - two Saudi, one Norwegian and one Emirati - were damaged on Sunday off the coast of the United Arab Emirates (UAE) in what Emirati officials described as acts of sabotage near the port of Fujairah.
The incident happened 140km south of the Strait of Hormuz, through which about one-third of all oil traded by sea passes.
"We ... talked about the policies that hardliners in the US administration as well as in the region are attempting to impose," Iran's Foreign Minister Zarif told Iranian state TV in India after a bilateral meeting with Foreign Minister Sushma Swaraj.
"We raised concerns over the suspicious activities and sabotage that are happening in our region. We had formerly anticipated that they would carry out these sorts of activities to escalate tension."