Hong Kong (CNN) The Chinese Ministry of Education has warned students to be careful if studying in the United States -- the latest sign of deteriorating relations between the two countries.

In its first "study aboard alert" of the year, issued on Monday, the ministry said students and academics must "prepare accordingly" if they wanted to study in the US.

"It has been the case for a while that some Chinese students who want to study in the US have been encountering visa restrictions, prolonged review times, shortened time validity and a rising rate of visa rejections," the ministry statement said.

"(This) affects Chinese students' successful study in the US."

The ministry rarely issues alerts of this nature -- and when it does they often relate to one university rather than an entire country.

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