Lawmakers in Washington have asked US Secretary of State Mike Pompeo to restore what they say is "visa fairness" for Chinese graduate students studying certain subjects in the US.

The State Department has implemented a policy that decreases the validity period of entry visas for Chinese graduate students studying aviation, high-tech manufacturing, and robotics at American colleges and universities from 60 months to 12 months. 

Democratic Congresswoman Grace Meng of New York, who was among 17 Democratic members of the House of Representatives who made the request in a letter to Pompeo on Friday, said that the policy impedes Chinese graduate students from being able to pursue educational opportunities during their studies outside of the US, and from being able to attend important functions such as a family reunion in China. 

"I'm deeply concerned by the State Department's decision to severely limit the validity period of entry visas for Chinese graduate students," Meng said in a statement on Friday. "The State Department is not applying this policy to students from other countries. Restricting the validity period is unfair and unwise, and it discriminates against these students based on their ethnicity. I urge Secretary Pompeo to reconsider this ill-advised policy."

The letter said that change targeting Chinese students is among other visa and immigration policy changes applied over the past year and a half that is making it difficult for US higher education institutions to attract the best and brightest students from around the world.

"We share your commitment to protect the security of US innovation, but solely focusing restrictions on Chinese students studying in certain technical fields absent any concrete evidence of wrongdoing wrongly stigmatizes them en masse as a national security threat," said a section of the letter.