The United Nations announced that a giant tanker dedicated to removing oil from a stranded ship off the Yemeni coast sailed from China Thursday on its way to Yemen, describing it as an "important" step in efforts to prevent a major spill.

In March, the United Nations Development Program bought the tanker "Nautica" to remove more than a million barrels of oil from the stranded ship "FSO Safer".

This was an unusual step taken by the UN organization, and was welcomed as a major advance in efforts to avert a potentially catastrophic oil spill.

Since the outbreak of Yemen's devastating civil war in 2015, Safer has been left deserted off the rebel-held port of Hodeidah, an important gateway for shipments into a country that relies heavily on emergency foreign aid.

The United Nations Development Program said in a statement that the Nautica left port on Wednesday after undergoing routine maintenance in Zhoushan, China.

A UN spokesperson said the vessel, which was bought by the major tanker company Euronav, is expected to reach its destination in early May and will make a stop on its way to make further technical adjustments.

"The departure of Nautica, and its voyage to the Red Sea, constitute an important next step in the complex operation of withdrawing oil from Safer," said UNDP Administrator Achim Steiner.

He called for urgent contributions to finance the operation, which still has a gap of about $34 million in its $129 million budget. The United Nations has launched a crowdfunding page that aims to raise $500,000.

"We are in a race against time. I urge government leaders, corporate CEOs and anyone in a position to contribute to come forward to support us in continuing to keep this process on track as it has quickly reached a critical point."

The statement cited "rising costs" for VLCCs such as Nautica due to the war in Ukraine.

"We have the best technical expertise available and the political support from all sides," said David Gresley, the UN Humanitarian Coordinator for Yemen.

"We just need the last bit of funding this month to ensure success" and prevent "catastrophe," he added.

The Safer tanker's load of 1.1 million barrels of oil is four times what was leaked in the "Exxon Valdez" disaster in 1989, which is considered the worst environmental disaster in the world, according to the United Nations.

An environmental catastrophe could also close the Bab al-Mandab Strait between Africa and the Arabian Peninsula, which would cause great damage to the global economy by closing the Suez Canal.