WASHINGTON -- US President Donald Trump said Monday the US forces have sunk all the Iranian mine-laying ships but it remains unclear if Iran has started laying mines in the Strait of Hormuz, through which a fifth of the world's oil passes.

"We don't know that they have dropped anything," Trump said at a press conference.

"With more than 30 mine-laying ships destroyed, we hit, to the best of our knowledge, all of their mine-laying ships," Trump claimed, while noting that Iran now can put mines on other types of ships and drop them in the strait.

Trump said the US military has struck more than 7,000 targets across Iran and "literally destroyed everything" on Iran's Kharg Island except oil facilities.

"As you know, we attacked Kharg Island and knocked it ... literally destroyed everything on the island except for the area where the oil is, I call it the pipes," Trump said.