A trade minister has travelled to China for an unpublicised visit this week at the same time as the head of the British military, the Guardian has learned.

Douglas Alexander, the minister for trade policy and economic security, is paying a visit to Beijing this week for talks with Chinese counterparts. He is also due to visit Hainan and Hong Kong.

Alexander’s trip, which does not appear to have been publicised anywhere by the UK or Chinese governments, coincided with an unannounced visit to China by Adm Sir Tony Radakin, the head of the British military, for the first time in a decade.

Alexander held talks with Chinese counterparts at a time when Beijing’s trade dispute with the US was intensifying, and while ministers have been locked in talks with British Steel’s owner, Jingye.

A government source said Alexander’s trip was pre-planned and unrelated to Donald Trump’s tariffs or the negotiations over the future of British Steel, with no talks planned with Jingye. The department said Alexander was promoting British exports and was due to give a speech at a Chinese consumer expo.

China’s defence ministry said Radakin had discussed strengthening military cooperation with a country that the UK officially describes as posing a “systemic challenge”.

Radakin met Gen Liu Zhenli, the chief of staff of China’s central military commission, on Wednesday, the defence ministry said in a short statement published on its website.

“The two sides conducted in-depth exchanges on China-UK relations and [military-to-military] relations, international and regional situations and issues of common concern, and had communication on strengthening exchanges and cooperation between the two militaries,” the ministry said.

British sources said it was in the country’s interest to maintain robust military communications with China – and to engage in “firm conversations” about the importance of peace in the Indo-Pacific.

Radakin posted a statement on X saying he and his Chinese counterpart had “held talks on a range of security issues” and “agreed that in an unstable world we must play our part as responsible nations with global interests, and we reflected on the importance of military-to-military communications”.

Some British politicians critical of China expressed surprise at Radakin’s visit. The former Conservative leader Iain Duncan Smith said his jaw had dropped when he learned about it.

“The Labour government is kowtowing to China, but they shouldn’t make the military follow them,” he said. “The most astonishing and alarming thing is to watch China being treated as an ally and friend, a country that trashed the Sino-British agreement on Hong Kong and has arrested peaceful democracy campaigners.”

Alistair Carmichael, a Liberal Democrat MP, said: “On any view this has got to be worrying because we know that China is not a trusted partner commercially and if you can’t trust them commercially then how can you trust them militarily?”

Frances D’Souza, a cross-bench peer and member of the all-party parliamentary group on Taiwan, said: “I have to say that it does not bode well for a robust UK policy on supporting a democratic Taiwan … This drives a hole through any possibility of having a coherent policy.”

It is the first time a UK chief of defence staff has visited China since 2015, when Britain was trying to foster a “golden era” of relations. The Chinese president, Xi Jinping, made a state visit to the UK the same year.

Relations have deteriorated since as China has aggressively asserted its control over Hong Kong, a former British colony. It has also been accused of spying on the UK and acting as a “decisive enabler” of Russia’s war in Ukraine by supplying components for munitions.

Labour has sought a rapprochement with Beijing since taking office. Two senior British ministers – the foreign secretary, David Lammy, and the chancellor, Rachel Reeves – have visited China in an effort to maintain positive economic relations despite the security concerns, with senior Chinese government figures paying visits to London as well. Reeves said a long-term relationship with China was “squarely in our national interest” on her trip in January.

Radakin is reported to have given a speech to students at the People’s Liberation Army National Defence University, which specialises in military education. The Times reported that he had defended the post-second world war security order and emphasised the value of alliances.

Trump introduced tariffs on China totalling 145% on imports to the US this week, prompting Beijing to retaliate with an 84% levy of its own. Beijing said on Thursday that a trade war would end in failure for the US after Trump had accused China of “ripping off the USA” with cheap imported goods.

The UK defence secretary, John Healey, co-hosted a meeting of defence ministers from 30 countries at Nato headquarters in Brussels on Thursday to discuss increasing pressure on Russia over Ukraine.

He told his counterparts: “We cannot jeopardise the peace by forgetting about the war. The daily reality for millions of Ukrainians continues, drone attacks, missile strikes, brutal fighting on the frontline, so we must put more pressure on President Putin to end his war and we must step up support for Ukraine.”

The discussions focused on planning for a “reassurance force” that could be deployed in Ukraine in the event of a peace agreement. The prospect of a ceasefire seems distant after Russia effectively rejected a US-backed proposal for a 30-day pause in hostilities.

The UK is to announce today that it will provide funding for a new £450m “surge” of military support for Ukraine as John Healey, the defence secretary, and his German counterpart host a meeting of 50 nations. Britain is providing £350m for drones and military repairs, while Norway will also contribute.

Addressing the group, Healey will say it is “vital to put Ukraine in the strongest possible position and pile pressure on Putin to help force him to end this terrible war”.

Reeves will travel to Poland on Friday for an informal meeting of European finance ministers to discuss defence spending. A Treasury source said: “A strong economy needs a strong national defence. That is why the chancellor will be travelling to Warsaw to make the case for deeper defence financing cooperation with our European allies so together we deliver greater economic and national security in a changed world.”

Russia carried out airstrikes against Kyiv earlier in the week, while Ukraine claimed to have captured Chinese nationals fighting for the Russian army. China’s foreign ministry said it was verifying the situation, but rejected Kyiv’s accusation that more Chinese citizens were involved in the fighting as groundless.