New Delhi: The ongoing diplomatic tussle between the United States and Iran has escalated to another level after US President Donald Trump on Wednesday came out with a stern warning to the middle east nation by stating that he had instructed the US Navy to destroy any Iranian gunboats if they harass American ships at sea.

"I have instructed the United States Navy to shoot down and destroy any and all Iranian gunboats if they harass our ships at sea," Trump tweeted on Wednesday, without providing other details, reported Xinhua news agency.

Deputy Secretary of Defence David Norquist said later at a Pentagon briefing that "all of our ships retain the right of self-defence and people needed to be very careful in their interactions to understand the inherent right of self-defence."

John Hyten, vice chairman of the Joint Chiefs of Staff, added at the same briefing that the US forces will respond with overwhelming lethal force to defend themselves if necessary.

"So if you cross that line, we know what that line is and we will respond. We don't need any more direction in order to do that. I think the president's message was crystal clear and we don't need any more actions," he said.

The US Navy said last week that 11 Iran's Islamic Revolution Guards Corps (IRGC) Navy vessels "repeatedly conducted dangerous & harassing approaches against US naval ships operating in international waters of the North Arabian Gulf."

The IRGC Navy, however, accused the U.S. naval forces of repeatedly "unprofessional" manner in the Gulf during recent weeks, threatening regional peace and given rise to new risks.

In a statement carried by Press TV on Sunday, the IRGC Navy said that the "illegal" presence of US forces in the region is the source of insecurity in West Asia.

"The only way to establish sustainable security in this region is the complete withdrawal of Americans from West Asia," said the statement.