The United States should be aware of the close military ties between Beijing and Moscow, China's defence minister said during a visit to Russia, which has been facing international isolation over the killing of a former spy in Britain.

In talks with his Russian counterpart, Sergei Shoigu, Wei said he wanted it made clear that his visit was a signal to “let the Americans know about the close ties between the armed forces of China and Russia”.

Wei was accompanied on his trip by China's foreign minister and senior diplomat Wang Yi, both of whom are newly appointed State Councillors.

Wang is expected to hold talks with his Russian counterpart, Sergey Lavrov, on Thursday.

Wei's bold comments came after Moscow expelled scores of diplomats from the US, Britain and other Western nations in retaliation for similar action taken against its envoys.

The row started after former Russian double agent Sergei Skripal and his daughter Yulia were poisoned in the British city of Salisbury. The pair remain in hospital in critical condition.

Yang Cheng, a Sino-Russian relations expert from Shanghai International Studies University, said the double visit by Wang and Wei suggested that Russia and China were considering regular “2+2 ministerial” meetings, a form of diplomatic talks involving both diplomatic and defence representatives.

“China and Russia already have an established diplomatic relationship, including top leadership, economic, defence and energy meetings,” he said. “A new mechanism like this could mean that both soft and hard strategies, previously talked about only internally, are discussed on a bilateral level.”

The timing of the visits was also significant, Yang said.

“It is important to reaffirm the Sino-Russian relationship after both Chinese President Xi Jinping and Russian President Vladimir Putin were confirmed as leaders for another term in March,” he said.

Putin is expected to visit China later this year.

China and Russia have tended to present a united front on international issues, which they see as a necessary counterbalance to the United States.

But talk of greater Sino-Russian military collaboration was more than just a gesture of solidarity for the benefit of Washington, said Artyom Lukin, a professor of international politics at Far Eastern Federal University in Vladivostok.

“Ever closer military cooperation is among the top priority directions for [the] Sino-Russian [partnership],” he said. “Russia has shown a willingness to sell China some of its most advanced weapons platforms, while China is becoming a major supplier of technologies and components, including electronics and naval ship engines, to Russia's military ... which has been deprived of Western technology.”

On the talks between Wang and Lavrov, Lukin said that North Korea was likely to top the agenda as Russia was keen to avoid making any moves that would contradict China's position.