A super-maglev train that can reach 1,000 kilometers an hour is in research and development in China, with experts warning that technical issues still need resolving before it becomes operational.

A proof-of-principle prototype for a 45-meter track has been developed by Deng Zigang and his team from the applied superconductivity laboratory at Southwest Jiaotong University in Chengdu, the China Central Television reported on Friday.

The train incorporates two technologies: maglev technology to eliminate wheel-rail friction and evacuated tube transport to remove air friction, according a thesis by Deng and his team that was published on the website of the Institute of Electrical and Electronics Engineers, a professional association based in the US.

Deng and his team have slashed air pressure in the tube to as low as 2.9 centibars, or 2.9 kilopascal units of pressure, in experiments on the 6-meter-diameter test run at a maximum speed of 50 kilometers per hour. Standard atmosphere pressure is 101.325 kilopascals.

The idea sounds exciting, but there are still technical problems to face including safety and cost, says Sun Zhang, a railway expert and professor at Shanghai Tongji University.

"The train has to be able to stop whenever needed," Sun told the Global Times on Sunday. "It can be achieved in the open air using air resistance, but could it be an issue in a vacuum tube where no resistance exists?

"What if the tube breaks and air enters the system? That could be another problem."

Japanese-made maglev trains traveled at a maximum speed of 603 kilometers an hour in 2015, The Guardian reported.

The Boring Company has received a verbal government approval to build an underground train that can travel between New York and Washington DC in 29 minutes, according to the twitter of company founder Elon Musk.