Tehran is prepared for a U.S. decision to end waivers granted to buyers of Iranian crude, an Iranian oil ministry source said on Monday, as the Revolutionary Guards repeated their threat to close the strategic Strait of Hormuz, Iranian media reported.

The United States will fail to cut Iranian oil exports to zero, the semi-official Tasnim news agency on Monday quoted an unnamed Iranian oil ministry source as saying.

U.S. President Donald Trump has decided not to reissue waivers in May allowing importers to buy Iranian oil without facing U.S. sanctions, the White House said in a statement on Monday.

Separately, the commander of the Revolutionary Guards’ navy said Iran would close the Strait if Tehran is barred from using it.

“According to international law, the Strait of Hormuz is a marine passageway and if we are barred from using it, we will shut it down,” the semi-official news agency Fars quoted General Alireza Tangsiri as saying on Monday.

“In case of any threat, we will have not even an iota of doubt to protect and defend the Iranian waters,” Tangsiri added.

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Tasnim quoted the unnamed source as saying: “Whether the waivers continue or not, Iran’s oil exports will not be zero under any circumstances unless Iranian authorities decide to stop oil exports ... and this is not relevant now.”

“We have been monitoring and analyzing all possible scenarios and conditions for the advance of our country’s oil exports, and necessary measures have been taken ... Iran is not waiting for America’s decision or the lack of it to export its oil,” Tasnim quoted the source as saying.”We have years of experience in neutralizing efforts by enemies to strike blows against our country,” the source added.

Iran has threatened to disrupt oil shipments through the Strait of Hormuz, a major oil shipment channel in the Gulf, if the United States tries to strangle Tehran’s economy by halting its oil exports.