Most debris from a large Chinese rocket expected to plunge back through the atmosphere this weekend will be burned up on reentry and is highly unlikely to cause any harm, Chinese foreign ministry spokesman Wang Wenbin said on Friday.

The U.S. military said on Wednesday what it called an uncontrolled re-entry was being tracked by U.S. Space Command.

The Long March 5B rocket blasted off from China's Hainan island on April 29, carrying the unmanned Tianhe module, which contains what will become living quarters on a permanent Chinese space station.

The location of the rocket's descent into Earth's atmosphere as it falls back from space "cannot be pinpointed until within hours of its reentry", which is projected to occur around May 8, U.S. Space Command said.

Harvard-based astrophysicist Jonathan McDowell told Reuters this week there was a chance that pieces of the rocket could come down over land such as in May 2020, when pieces from another Chinese Long March 5B rocket rained down on the Ivory Coast, damaging several buildings.

He said potentially dangerous debris would likely escape incineration after streaking through the atmosphere at hypersonic speed but in all likelihood would fall into the sea, given that 70% of the world is covered by ocean.

Speaking in Beijing, Foreign Ministry spokesman Wang Wenbin said China was closely following the rocket's reentry into the atmosphere, and that most of its components would be burned up upon re-entry.

"The probability of this process causing harm on the ground is extremely low," he said.

Debris from the Long March 5B is likely to fall in international waters, China's Global Times reported on Wednesday.

Based on its current orbit, the debris trail is likely to fall somewhere as far north as New York, Madrid or Beijing and as far south as southern Chile and Wellington, New Zealand, or anywhere in between, McDowell said.

The Tianhe launch was the first of 11 missions needed to complete the Chinese space station.