The government has stated that it wants "stable and pragmatic engagement" with China, and Sir Keir Starmer is scheduled to see President Xi Jinping at the G20 summit in Brazil.

This will be the first in-person encounter between a UK prime minister and the Chinese president since 2018.

Sir Keir will say it is right to engage with China on "areas of mutual cooperation" such as international stability, climate change and economic growth.

But Downing Street said he would also "be firm on the need to have honest conversations on areas of disagreement," and that engagement would be "rooted at all times in the UK's national interests".

Speaking to reporters on his way to the summit in Rio de Janeiro, Sir Keir said "shoring up support for Ukraine" was top of his agenda.

Downing Street says the prime minister will urge other G20 nations to step up their support for Ukraine or face "unfathomable consequences" if Russia is allowed to be victorious.

The summit follows large-scale missile and drone attacks by Russia across Ukraine over the weekend, and will take place as the conflict approaches its 1,000th day.

And it comes amid reports that the US has authorised the use of long-range missiles it supplies to Ukraine to strike Russia.

The weapons have so far only been used by Kyiv on Russian-occupied targets within its own territory.

The UK has also supplied Ukraine with its Storm Shadow missiles and defence officials and ministers have for months been making the case for Kyiv to be permitted to use them to hit targets inside Russia. But they were not willing to act alone - and had been waiting for the White House to change its mind.

Downing Street has not directly commented on the reports about the US decision.