"Am I thinking about it? Absolutely. But there's no planning yet until the political decision is taken," US General Alexus Grynkewich, NATO's Supreme Allied Commander Europe, told journalists.

US President Donald Trump has blasted Washington's European allies in NATO for their response to his war on Iran -- which has seen the crucial waterway closed.

European countries spearheaded by Britain and France have been scrambling to put together a possible plan for how they could help keep the strait open if the war ends.

So far US-led alliance NATO has steered clear of seeking any direct involvement in the conflict -- despite pressure from Trump.

"Each nation is considering their response, with many, including Belgium, France, Germany, Italy, and the United Kingdom, sailing ships to the region," Grynkewich said.

"We all agree it's in our interest to ensure freedom of navigation in international waters."

European diplomats at NATO have played down of the prospect of the alliance playing a major role in the strait given internal divisions.

But they say it could be involved in some way in any eventual operations led by France or Britain if they materialise.

The closure of the Strait of Hormuz has had a major impact on global energy prices and is already taking a toll on economies in Europe.