The Foreign Ministry confirmed on Wednesday that a Chinese delegation's absence at the 70th International Astronautical Congress in Washington was due to a visa issue, and it urged the United States not to "weaponize" visas and hinder normal international cooperation.

The U.S. did not issue a visa for the delegation in time, ministry spokeswoman Hua Chunying said at a daily news conference.

According to Hua, China had given to the U.S. a list of attendees in July, and the visa interview process took place in the U.S. embassy in Beijing on Oct 12.

But the head of delegation still had not received his visa as the congress began on Monday. Because of this, Hua said, the Chinese delegation is absent at the opening and some other activities of the congress.

Several other Chinese delegates also did not get visas, she added.

The congress in the U.S. capital will end on Friday.

China has always championed multilateral cooperation in space exploration and actively participates in the conference every year, Hua said.

A speech given by U.S. Vice-President Mike Pence at the opening of the congress was poorly received by the audience.

About 200 people from the U.S. astronautical community signed a letter that said, "Welcoming Vice-President Pence to open this year's IAC is at odds with the IAC's purported mission of global collaboration".

The visa problem encountered by the Chinese delegation is only the "tip of the iceberg", Hua said.

For quite a while, she said, the U.S. has been denying visas, delaying processing times and revoking long-term visas for Chinese scholars, students, entrepreneurs and scientists.

Such moves have thwarted normal people-to-people exchanges between China and the U.S. and have infringed upon the safety and lawful rights and interests of the Chinese personnel involved, she said.

The U.S. has repeatedly disregarded international obligations and disrupted normal international exchanges, Hua said, adding that Washington should sincerely reflect on and earnestly correct its wrongdoings.