Military conflict with Iran should be the last resort amid escalating tensions, but the United States has the ability to set back Tehran's nuclear capability by a decade, according to Trump attorney Rudy Giuliani.

If America had to strike Iran, the United Kingdom should help or take itself out of the North Atlantic Treaty Organization (NATO), the former New York City mayor claimed Friday on "Hannity."

IRAN'S REVOLUTIONARY GUARD SEIZES UK-OPERATED TANKER IN STRAIT OF HORMUZ

"We could set them back five or ten years," he said. "I'd be happy with that. If we had to hit them back -- and I agree that should be the last resort -- we could do serious damage to all of their nuclear facilities.

"The British should help us with that, or they should resign from NATO."

Iran seized a British-flagged oil tanker in the Strait of Hormuz earlier Friday and briefly detained a second, marking a fresh escalation of tensions between Tehran and the West.

The U.K.-flagged Stena Impero “was approached by unidentified small crafts and a helicopter during transit of the Strait of Hormuz while the vessel was in international waters,” Stena Bulk, the shipping company that owns the vessel, said in a statement.

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Iran's Revolutionary Guard forces, in a statement on their website, say the ship was seized for "non-compliance with international maritime laws and regulations" and is being brought to an unnamed Iranian port, according to the Associated Press. Websites tracking the ship's path showed it turn sharply in the direction of Iran's Qeshm Island, instead of its intended destination of Saudi Arabia.

Stena Bulk says "there have been no reported injuries and their safety is of primary concern to both owners and managers."

Fox News' Greg Norman contributed to this report.