Tony Blair today warned the presidents of Venezuela and Bolivia to "behave sensibly" as they take more control of their country's energy sectors.
The prime minister said energy was a concern to the entire global community and the important thing was for everyone to "use the power they have responsibly".
"People are worried about energy supply in the future. What countries do in their energy policy ... matters enormously to all of us," he told an EU-Latin America summit in Vienna.
He was speaking after Bolivian president Evo Morales indicated that, following his announcement that he would be nationalising his country's gas industry, foreign firms such as BP and British gas may not be compensated.
Venezuela's Hugo Chavez has also indicated that he would impose additional taxes on international companies - moves that have raised concern in the US in particular, as the White House regards Latin America as very much in its sphere of interest.
The relationship between Mr Blair and Mr Chavez is similarly difficult - in February, responding to the president's new alliance with Cuba, the British prime minister called on the president to "abide by the rules of the international community".
This prompted the left-wing Mr Chavez to demand the return of the Falkland Islands, saying that the British occupation showed the UK was not fully compliant with international law.
Mr Chavez is visiting London this weekend, but will not be visiting Downing Street - something No 10 insisted was because the president was making a private, not official, trip to the UK.
However, Mr Chavez will be meeting with union leaders, MPs and London mayor Ken Livingstone, who this morning praised him as a "beacon of democracy and social progress in Latin America".
"Latin America is an increasingly important world economic region and London's future depends of establishing strong links with the world's great emerging economies," Mr Livingstone said.
"Venezuela is an important country economically in the region, and one of the world's largest oil exporters.
"However, it is not only for economic reasons that I am delighted to welcome president Hugo Chavez of Venezuela to London next week ... since 1998 he has won ten elections in eight years - an unprecedented record of electoral success in any country."
After visiting Mr Livingstone on Sunday, Mr Chavez will meet TUC leaders on Monday before having lunch with a series of celebrities, media types and MPs at City Hall.