Iran's Foreign Minister Mohammad Javad Zarif has slammed the US for its unbridled support for Saudi Arabia in its war of aggression against Yemen, saying Washington is complicit in the world's biggest humanitarian disaster.

In a post on his official Twitter account on Thursday, Zarif said the role that the United States has so far played in fanning the flames of the Yemen war, including through supplying Saudi Arabia with bombs and refueling its warplanes, is apparently not enough for American rulers.

By acknowledging involvement in managing brutal Saudi airstrikes, the US is complicit in the world’s biggest humanitarian disaster, he added.

It's official: Supplying bombs, targets and refueling #Saudi warplanes is apparently not enough. US now proclaiming that it's "doing the planning" in war on #Yemen too. US complicity in world's biggest humanitarian disaster unfathomable. — Javad Zarif (@JZarif) March 29, 2018

The remarks came two days after Pentagon chief James Mattis said the US military was “doing the planning” of Saudi Arabia’s military campaign against Yemen. “So this is a very dynamic sort of battlefield management,” he added.

Mattis further admitted US involvement in mid-air refueling of Saudi warplanes, claiming that the operation could help minimize civilian casualties in the war-torn country.

The Saudi aggression was launched in March 2015 in support of Yemen’s former Riyadh-friendly government and against the country’s Houthi Ansarullah movement, which has been running state affairs in the absence of an effective administration.

The offensive has, however, achieved neither of its goals despite the spending of billions of petrodollars and the enlisting of Saudi Arabia's regional and Western allies.

The Saudi-led campaign, which is accompanied by a land, aerial and naval blockade of Yemen, has so far killed and injured over 600,000 civilians, according to the latest figures released by the Yemeni Ministry of Human Rights.

Last December, several UN agencies raised the alarm about the humanitarian situation in Yemen, saying about 75 percent of Yemen’s population is in need of humanitarian assistance.

“The conflict in Yemen has created the worst humanitarian crisis in the world, a crisis which has engulfed the entire country,” the agencies said.