Venezuelan President Hugo Chavez has begun a private visit in Britain.
President Chavez has criticised the UK's support of the US
The left-wing leader is meeting the Mayor of London Ken Livingstone, as well as some Labour MPs and union leaders during his two-day trip.
But he will not meet Prime Minister Tony Blair, whom he has called a pawn of the "imperialist" US.
Mr Chavez controls a country with the world's fifth largest oil supply. On Friday Mr Blair urged Venezuela to use its energy resources responsibly.
BBC World Affairs correspondent Chris Morris says Mr Chavez is following in the footsteps of Cuban leader Fidel Castro.
Mr Chavez - a fierce critic of the US - has been spearheading a drive in Latin America for countries to nationalise their energy supplies.
The campaign has taken root in Bolivia, which has unveiled plans for greater state control of its natural gas wealth.
Chavez supporters showed their delight at his visit
Mr Chavez is giving a talk on Venezuelan social reform on Sunday.
On Monday he will have lunch with Mr Livingstone, and will deliver a lecture in the evening.
On a previous trip to the UK in 2001 Mr Chavez warmly embraced Mr Blair, but has since fiercely criticised the UK's support for the war in Iraq.
Mr Blair's office has said a meeting was not requested this time and that Mr Chavez's visit was "private".
Mr Chavez arrived from the European-Latin America summit in Vienna.
While in Vienna, he said he would like to provide cheap heating oil for Europeans on low incomes as he had to needy Americans in the eastern US this winter.
Mr Blair also attended the summit, where he said Venezuela and Bolivia should act responsibly with their resources.