Iranian Supreme Leader Ayatollah Ali Khamenei on July 21 backed President Hassan Rohani's suggestion that Iran may block oil exports from the Persian Gulf if its own exports are stopped.

Khamenei's website said Khamenei supported Rohani's statement earlier in July that "if Iran's oil is not exported, no regional country's oil will be exported."

The website said Rohani's comments were "important remarks that reflect the policy and the approach of [Iran's] system."

Rohani's apparent threat to disrupt oil shipments from neighboring countries came in reaction to imminent U.S. sanctions and efforts by Washington to force all countries to stop buying Iranian oil.

Iranian officials have in the past threatened to block the Strait of Hormuz, the oil sea passage from the Persian Gulf to the open ocean and one of the world's most strategically important choke points, in retaliation for any hostile U.S. action.

If the Strait of Hormuz was successfully blocked at its narrowest point, a 54-kilometer wide waterway between the coasts of Iran and Oman, it would cut off sea shipments of oil by Iraq, Saudi Arabi, Bahrain, Qatar, and the United Arab Emirates.

The Gulf coastal areas of those countries contain the largest source of crude oil in the world.

Tehran has harshly criticized the decision in May of U.S. President Donald Trump to unilaterally pull the United States out of the 2015 nuclear deal between Iran and six world powers and reimpose sanctions.

Khamenei told officials in Iran's Foreign Ministry earlier on July 21 that it would be an "obvious mistake" to negotiate with the United States because Washington is unreliable.

"The word and even the signature of the Americans cannot be relied upon, so negotiations with America are of no avail," Khamenei’s official website quoted him as saying.

During the past week, with Khamenei and other hard-liners questioning whether Tehran should continue honoring its obligations under the nuclear deal after Trump’s decision, Iran announced it is continuing to acquire uranium and is close to finishing a plant where it can build more centrifuges to enrich uranium.

Vice President Ali Akbar Salehi, who heads the Iranian Atomic Energy Organization, said Iran will continue adhering to the nuclear deal and that the country's stepped up nuclear activities will remain within the limits set by the accord.

Iran also filed a lawsuit at the International Court of Justice (ICJ) against the United States on July 18 in response to Trump’s decision.

Iran says its nuclear program is strictly for civilian purposes, while Washington has accused it of attempting to develop nuclear weapons.

Trump said during a NATO summit earlier in July that with the U.S. increasing sanctions on Iran, he expected Iranian negotiators “at a certain point” to “call me and say, 'Let's make a deal,’ and we'll make a deal."

But Iran’s Foreign Ministry responded by saying that if Trump wants to negotiate after pulling out of the international agreement, he would have to "initiate the call himself" because Iran’s top leadership is now rejecting any talks with the United States.

With reporting by Reuters, AP, AFP, Al-Jazeera, and Tasnim