WASHINGTON, March 13 (Xinhua) -- The United States will not allow shipping in the Strait of Hormuz "to be contested" by Iran, U.S. Defense Secretary Pete Hegseth said Friday.

There is no clear evidence that Iran has placed mines in the Strait of Hormuz, he said at a news briefing.

He said the United States is planning for Iran's various measures and "that's not a strait we're gonna allow to remain contested."

The Strait of Hormuz, a narrow waterway that connects the Gulf and the Gulf of Oman, is one of the world's most critical maritime chokepoints, carrying around a quarter of global seaborne oil trade and significant volumes of liquefied natural gas and fertilizers.

Hegseth also told reporters that strikes carried out by the United States and Israel have significantly weakened Iran's military capabilities.

"Between our Air Force and that of the Israelis, over 15,000 enemy targets have been struck," he said.

Iran's missile volume is down 90 percent and that of their one-way attack drones was down 95 percent as of Thursday, Hegseth further said.

Hegseth threatened that "today will be yet again, the highest volume of strikes that America has put over the skies of Iran and Tehran."

Hegseth also told reporters that the U.S. Central Command has designated an investigating officer to complete a command investigation into a strike on an elementary school in Iran that killed over 160 people, mostly pupils.

The Feb. 28 strike on Shajarah Tayyebeh elementary school in Minab occurred during U.S. operations targeting a nearby Iranian military base. According to reports, a preliminary finding from an ongoing military investigation indicates that the school was struck by a U.S. Tomahawk missile.