In signs of a new diplomatic spat, China says the United States is violating the Vienna Convention by requiring Chinese diplomats in the US to give official notice before they visit universities and research institutions or meet local government officials.
"According to... the Vienna Convention, the receiving state shall accord full facilities for the performances of the functions of the mission," the Chinese embassy in the US said on Twitter. "But the US side is doing exactly the opposite."
The comment came in response to the American announcement on Wednesday of the notification requirements.
State Department officials briefing journalists on a conference call said the move mirrored requirements placed by China on US diplomats in China - a claim that China's Foreign Ministry spokesman Geng Shuang told reporters was "simply groundless".
China consistently supported US diplomats in the country, Mr Geng told reporters in Beijing. "We urge the US to correct its mistakes, revoke the relevant decision, and provide support and convenience to Chinese diplomats in the US... rather than artificially setting up barriers," he said.
It was unclear what requirements US diplomats face in China. But the State Department officials said US diplomats there do not have unfettered access to local and provincial-level officials, academic institutions and research institutes.
"We've been complaining informally and through formal channels to the Chinese for years now about limits on access of US diplomats to various stakeholders... in China," one official said.
"I would say that the Chinese response is, 'We give you access when it's appropriate,' and that clearly is not something that goes down well with us," he said.
The Chinese embassy in Washington was informed of the new requirements over the past week, the officials said. "We are not restricting Chinese access to stakeholders here in the United States," they insisted. "We are not forcing them to seek permission. We're merely asking them to notify."
One official said: "We absolutely value educational and cultural exchange. We absolutely encourage state and local officials, as well as educational and research institutions, to meet with and host foreign officials as they deem appropriate. We are not requiring that any Chinese official get permission from the State Department to have any of these sorts of meetings.
"We're merely asking that they notify us in advance.
"That's different from what happens many times in China, where our diplomats are forced to seek permission and are often denied such permission.
"Our goal is to get the Chinese authorities to allow our diplomats in China to engage with provincial and local leaders, Chinese universities, and other educational and research institutes freely, the same way that the Chinese diplomats are able to do here."
The State Department's move appears to be part of a suite of measures against China across a broad front, from tariffs on Chinese imports to new scrutiny of Chinese activity in the US, including investments particularly in technology, and the role of educational institutions such as Confucius Institutes.
The officials did not specify what measures would be taken against diplomats who did not comply.
In reply to a question, they reiterated that "there's a clear gap between the way our US diplomats are able to do their job in China versus the liberties that Chinese diplomats posted here in the United States are able to do their job".
One official said: "What we're looking to do is impose a little bit of reciprocity."