In a statement responding to US accusations that Iran has been carrying out increased attacks on commercial shipping, Iranian Foreign Ministry spokesman Nasser Kanaani said Iran plays the "most effective" role in ensuring maritime security in regional and international waters and has always been a "guarantor" of the "harmless and safe" passage of ships and vessels across the Strait of Hormuz.
The spokesman condemned the US government for “compromising maritime security by breaking maritime law and seizing certain Iranian oil shipments in international waters and high seas.”
Iran seized the Marshall Islands-flagged Advantage Sweet on April 27 as it traveled in the Gulf of Oman. Six days later, it seized a second ship, the Niovi, a Panama-flagged tanker as it left a dry dock in Dubai.
On Friday, US National Security Council spokesman John Kirby said Washington has seen "repeated Iranian threats, armed seizures, and attacks against commercial shippers who are exercising their navigational rights and freedoms in international waterways."
Kirby added that in the coming weeks there would be an attempt to "increase coordination and interoperability" with allies in the Strait of Hormuz.
The Strait of Hormuz, a crucial waterway for global energy supplies, has often been a site of tense encounters between Americans and Iranian forces.
In early December, an Iranian patrol boat tried to temporarily blind US Navy ships in the Strait of Hormuz by shining a spotlight toward the vessels and crossing within 150 yards of them.
Last August, an Iranian ship seized an American military unmanned research vessel in the Gulf but released it after a US Navy patrol boat and helicopter were deployed to the location.
Iran recently said it had "forced" a US submarine to surface as it was crossing the Strait of Hormuz.
The Islamic Republic has threatened more than once to close the Strait of Hormuz, with the United States warning Iran in response that any attempt to close the strait would be viewed as a "red line" -- grounds for US military action.