Boris Johnson says the UK’s extradition arrangements with Hong Kong will be changed, amid rising tensions with China.
Foreign Secretary Dominic Raab is expected to suspend an extradition deal with the territory later.
It comes after Beijing imposed a controversial national security law on the ex-British colony, introducing new crimes with severe penalties.
China has accused the UK of “brutal meddling” in its affairs.
The UK has already offered residency rights and a path to UK citizenship to around three million Hong Kongers in response to the law’s imposition.
Beijing has insisted it is committed to upholding international law, and has promised a “resolute response” if the UK withdraws from extradition arrangements.
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The extradition treaty means that, if someone in Hong Kong is suspected of a crime in the UK, then the British authorities can ask Hong Kong to hand them over to face justice – and vice versa.
The UK fears the arrangement – which has been in place for more than 30 years – could see anyone it extradites to Hong Kong being sent on to China.
Hong Kong has extradition agreements with 19 other countries apart from the UK, including Canada and Australia, which have already suspended theirs following the imposition there of China’s new security law – which makes acts of subversion punishable by life sentences.
Mr Johnson said the UK had “concerns” over the new law, and it had to think about the rights of people in Hong Kong to participate in democratic processes.
But he added: “There is a balance here. I’m not going to be pushed into a position of becoming a knee-jerk Sinophobe on every issue, somebody who is automatically anti-China”.
“We’ve got to have a calibrated approach. We’re going to be tough on some things, but we’re going to continue to engage.”
The UK handed Hong Kong back to China in 1997 but, as part of an agreement signed at the time, it enjoys some freedoms not seen in the mainland.
But political and economic relations between the UK and China have become strained in recent months.
Earlier this month, the UK decided to ban Chinese tech firm Huawei from its 5G network, citing security concerns denied by the company.
The UK, US and EU have accused Beijing of undermining the “One Country, Two Systems” principle, which has guaranteed a high degree of autonomy for Hong Kong since it was handed back to Chinese rule in 1997.
They say the security laws which came into force last month breach the terms of the 1984 Joint Declaration protecting political and economic freedoms – which agreed the conditions under which Hong Kong would be run when Britain gave it back to China in 1997.