Kenya's President and ICC indictee Uhuru Kenyatta will meet UK Prime Minister David Cameron during a three-day visit to London, his office says.
A Kenyan rights group has condemned the visit - his first to a Western nation since his election in March.
The UK had said it would maintain only essential contact with Mr Kenyatta, but has invited him to London to attend a conference on the Somalia conflict.
He denies International Criminal Court charges of crimes against humanity.
The charges relate to Mr Kenyatta's alleged role in violence that killed about 1,000 people after the disputed 2007 election.
He is due to appear at the ICC for his trial in The Hague in July.
Mr Kenyatta beat then-Prime Minister Raila Odinga by 50.07% to 43.28% in the March election.
In a statement, Mr Kenyatta's office said he had arrived in London on Monday morning.
"During the visit, President Kenyatta will attend the London conference on Somalia and also hold bilateral meetings with UK Prime Minister David Cameron and other UK government officials," it added.
The executive director of Kenya's International Center for Policy and Conflict lobby group, Ndung'u Wainaina, said the invitation to Mr Kenyatta "betrays the agenda" of the Somalia conference, which is to root out impunity and insecurity.
The BBC's Karen Allen says the UK had been agonising about how to invite Mr Kenyatta without losing face after warning before the election that it would have only "essential contact" with him if he was voted into power.
UK officials note that Mr Kenyatta is co-operating with the court - unlike Sudan's President Omar al-Bashir.
A UK foreign office spokesman said it was "right" that Kenya should be represented at the conference and that this did constitute "essential contact".
Kenya provides nearly 5,000 troops to an African Union (AU) force in Somalia and is the UK's most important ally in East Africa, our correspondent says.
Delegates from more than 50 countries and international organisations are expected to attend the conference on Tuesday.
It follows a similar conference hosted by Mr Cameron last year to help Somalia rebuild itself.
The al-Qaeda-linked militant group al-Shabab lost control of Somalia's capital, Mogadishu, to AU and Somali government forces in 2011.
However, it still controls many rural areas and has carried out a series of bombings in Mogadishu.
Piracy is also a major problem off Somalia's coast.