US Pledges to Use Strait of Hormuz Amid Iran’s Threat to Close it - State Dept.

"Iran on a fairly regular basis makes sort of extortionist threats and blackmail demands. This is part of the regular course of their business," Hook said. "They've threatened to close the Strait of Hormuz more times than I can count. The United States military will fly, sail and operate wherever international law allows, that's partly to ensure protection of the global commons so that it can be safe for commercial and noncommercial traffic."

The comment referred to the Monday's statement by the head of the Revolutionary Guard Corps navy force, Alireza Tangsiri, who said that Iran will close the Strait of Hormuz if the country is unable to use it, according to Fars News Agency.

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The Strait of Hormuz, a narrow stretch of water between the Persian Gulf and Gulf of Oman, is considered one of the world's most important choke points for world oil supplies. More than 18 million barrels of oil pass through the narrow waterway each day, accounting for 30 percent of the world's oil shipments by sea, according to the US Energy Information Administration.

Iran's statement regarding the Strait of Hormuz came in response to the US decision to end its sanctions waivers for importers of Iranian oil starting on 2 May. Washington's aim is to eventually cut Iranian oil imports to zero, which is likely to have a significant impact on the country, where oil exports serve as one of the main sources of revenue.

Previously, US economic sanctions on Iran had been lifted as part of the nuclear agreement. But in May 2018 US President Donald Trump announced his country's withdrawal from the deal and the reinstatement of sanctions.