The prime minister has arrived in Johannesburg in South Africa for a gathering of world leaders at the annual G20 summit.

The summit brings together the 20 biggest economies, although Donald Trump has decided not to attend over widely discredited claims that white people are being persecuted in the country.

Sir Keir Starmer, whose critics label him "never here Keir" because of the frequency of his international trips, has emphasised the benefits of a prime minister acting as an ambassador for UK businesses abroad.

Downing Street has also said the visit will be used to engage with allies to strengthen support for Ukraine.

Sir Keir joined French President Emmanuel Macron and German Chancellor Friedrich Merz on a call with Ukrainian President Volodymyr Zelensky, where they discussed a US-backed peace plan.

In a post on X, Zelensky said: "We value the efforts of the United States, President Trump, and his team aimed at ending this war. We are working on the document prepared by the American side. This must be a plan that ensures a real and dignified peace."

He added that the leaders were "co-ordinating closely to make sure that the principled stances are taken into account".

There is deep concern about some of the reported proposals, which appear to reflect many of Moscow's demands.

Under a widely leaked draft plan, Kyiv would cede significant areas of the Donetsk region of eastern Ukraine that it still controls, cut the size of its army, and pledge not to join Nato - proposals it has previously ruled out.

Before the summit formally opens, Sir Keir will visit a Johannesburg depot to see trains that were built in Derby and announce a new deal where the UK will "provide strategic advice and consultancy services" to South Africa's railways.

An organisation called Crossrail International, which is owned by the UK government, will carry out the work.

It has also signed a deal with Vietnam to provide similar services there.

Downing Street argues that Africa provides what it calls "unparalleled future opportunities for UK businesses" given half of Africans are under the age of 20 and more than a quarter of the world's population will live in Africa by 2050.

"I will focus on the deals we can do, the business we can do, with our partner countries and make sure that the work we do internationally is impacting directly at home," he told reporters on the flight to South Africa.

"If you want to deal with the cost of living and make people better off with good secure jobs, investment from G20 partners and allies is really important," he added.

Trump will skip the summit, after declaring it a "total disgrace" in a post on social media, and repeating his claim that white Afrikaners are being persecuted in South Africa.

White South Africans have been offered refugee status in the US by the Trump administration, and currently have priority over ethnic groups.

South Africa's President Cyril Ramaphosa said the absence of the US at G20 was "their loss" and added that "boycott politics doesn't work".

None of South Africa's political parties - including those that represent Afrikaners and the white community in general - have claimed that there is a genocide in South Africa.