Image copyright Getty Images Image caption The two economic giants have been fighting a trade war over the past year

Chinese diplomats in the US will have to notify American authorities before holding any meetings with US officials.

Official visits to "educational and research institutions", such as schools and universities, must also be pre-registered, the state department said.

China said the US was breaking international rules - but the US said American diplomats in China faced similar restrictions.

The move comes amid heightened tensions between both countries.

What did the US say?

The rules would apply to "official meetings with [US] state officials, official meetings with local and municipal officials, official visits to educational institutions, and official visits to research institutions", the state department said.

An official said the US was merely "levelling the playing field" with China, and that it was a response to Chinese restrictions on American diplomats.

"In China, US diplomats do not have unfettered access to a range of folks that are important for us to do our job here.

"In contrast, [Chinese] diplomats in the US are of course, able to take full advantage of our open society," said a senior state department official.

US officials said Chinese diplomats did not need permission for the meetings, but were required to notify the state department in advance.

The eventual goal, said the official, would be for "these requirements and the requirements on US diplomats in China [to] both be disbanded."

How did China respond?

In a statement on Thursday, the Chinese Embassy in US called the new rules a "violation of the Vienna Convention".

"The Chinese side does not have similar requirements on American diplomats and consular officers in China," it insisted.

It added: "As for reciprocity, the US has a far greater number of diplomatic personnel in China than China has in the US."

What is the Vienna Convention?

The Vienna Convention is an agreement that outlines the rules of diplomatic relations.

Under this convention, diplomats are "ensured" freedom of movement and travel in their host countries.

The convention also says the receiving state "shall not discriminate as between states".

What is the background to this?

The two countries have been fighting a trade war, imposing tariffs on billions' worth of each other's goods over the past year.

Media playback is unsupported on your device Media caption Will a trade deal end US-China rivalry?

However, the state department official said the new ruling was "not directly linked" to the trade war with China.

US President Donald Trump has long accused China of unfair trading practices and intellectual property theft. While in China, there is a perception that the US is trying to curb its rise.