Foreign Secretary Dominic Raab confirmed the widely expected move in parliament, despite Chinese warnings that Britain was making a grave foreign policy error and risked reprisals.

He also announced an extension to Hong Kong of an arms embargo of "potentially lethal weapons" already in force against mainland China for the last three decades.

Diplomatic ties between London and Beijing have been frayed by the security law, which Western powers see as an erosion on civil liberties and human rights in the financial hub.

China threatened unspecified counter-measures after Britain relaxed immigration rules for Hong Kongers with British overseas passports, and the potential of citizenship.

Adding to the tensions have been British criticisms about China's treatment of the Uighur ethnic minority group, and the blocking of telecoms giant Huawei from its 5G networks.

Raab said Britain wanted to engage constructively with China, acknowledging its "extraordinary transformation" and the key role it had to play in world affairs.

But he said a positive relationship with a country that had international obligations as a global player also included the right to disagree.

The security law had "significantly changed key assumptions underpinning our extradition treaty", particularly a provision to try certain cases in mainland China, he said.

The legislation does not provide legal or judicial safeguards, and there was concern about its potential use in the former British territory, he added.

"The government has decided to suspend the extradition treaty immediately and indefinitely," he said.

"We would not consider reacting to it unless and until there are clear and robust safeguards."

- Arms embargo -

Raab said there was also cause for concern about the extent to which China was playing a role in law enforcement and internal security in semi-autonomous Hong Kong.

"The UK will extend to Hong Kong the arms embargo that we've applied to mainland China since 1989," he told lawmakers.

"The extension of this embargo will mean that there will be no exports from the UK to Hong Kong of potentially lethal weapons, components or ammunition.

"And it will also mean a ban on the export of any equipment already banned, which might be used for internal repression."

Wang Wenbin, spokesman for China's foreign ministry, earlier warned Britain of reprisals for meddling in its internal affairs, and called criticisms of its Uighur policy "slander".

"We urge the UK not to go further down this wrong path, in order to avoid further damage to China-UK relations," Wang said.

"Recent erroneous remarks and measures concerning Hong Kong have seriously violated international law and basic norms governing international relations...

"China strongly condemns this and firmly opposes it."

Britain's extradition treaty suspension comes after similar tough action against China by the United States, Canada and Australia.

Beijing has accused London of being a puppet to US foreign policy over Huawei, after Washington slapped sanctions on the Chinese firm's access to US chips vital to its 5G networks.

The United States believes the private firm is a front for the Chinese state, and that the use of its technology could imperil intelligence sharing, charges that the company denies.

The issue is likely to loom large during US Secretary of State Mike Pompeo's visit to London on Tuesday.