Rishi Sunak urges Russia to 'get out' of Ukraine at G20
Rishi Sunak has urged Russia to "get out of Ukraine," as he condemned its "barbaric" invasion at the G20 summit of world leaders.
At a meeting attended by Russia's foreign minister Sergei Lavrov, the British PM said the UK would "back Ukraine for as long as it takes".
Mr Sunak criticised Russian President Vladimir Putin for not turning up to the summit held in Indonesia.
"Maybe if he had, we could get on with sorting things out," he added.
Mr Sunak is attending the summit for the first time as UK prime minister, after replacing former Conservative leader Liz Truss last month.
war in Ukraine is set to dominate the conference of major world economies, taking place in the Indonesian island of Bali this week.
Speaking at a closed-door session for world leaders, Mr Sunak blamed the conflict in Ukraine for worsening economic conditions globally. 
He said Russia's "weaponisation" of energy and food exports was harming the world's poorest.
He added that "countries should not invade their neighbours", accusing Russia of undermining "fundamental principles of sovereignty and territorial integrity". 
"It is notable that Putin didn't feel able to join us here. Maybe if he had, we could get on with sorting things out," he added.
"The single biggest difference that anyone could make is for Russia to get out of Ukraine and end this barbaric war."
Mr Lavrov is representing Russia - a G20 member - at the summit after Moscow said President Putin would not be attending. 
In a video speech earlier, Ukrainian President Volodymyr Zelensky urged leaders to extend a UN-backed grain export deal due to expire on Saturday.
greement, struck in July, saw Moscow agree to allow ships to export millions of tonnes of grain and other foodstuffs from Ukraine through a safe corridor in the Black Sea.
Russia said on Saturday that there had yet to be any agreement to extend the deal.
In return for allowing Ukraine to ship out food, it has insisted the West lifts sanctions on a state-run agricultural bank, which it argues has effectively blocked Russian food and fertiliser exports.
Meanwhile, Mr Sunak has said China poses a "systemic challenge" to the UK.
His predecessor Ms Truss was reportedly planning to designate the country a "threat" to the UK as part of a foreign policy review. 
Asked whether he would do the same, Mr Sunak told reporters: "I think that China unequivocally poses a systemic threat - well, a systemic challenge - to our values and our interests and is undoubtedly the biggest state-based threat to our economic security.
"But I also think that China is an indisputable fact of the global economy and we're not going to be able to resolve shared global challenges like climate change, or public health, or indeed actually dealing with Russia and Ukraine, without having a dialogue with them."