Luiz Inacio Lula da Silva, the Brazilian president said: "The prime minister and I agreed that, as soon as possible, it would be good to hold a meeting of heads of state and government to give a decisive push" to the Doha round of World Trade Organisation (WTO) talks.
He was speaking on Thursday at the end of a three-day state visit to Britain.
Tony Blair, the British prime minister, speaking alongside Lula after talks in Downing Street, said: "We are prepared to have a meeting of the key leaders and we'll discuss with our colleagues how and when that can be possible."
Blair and Lula issued their appeal on the eve of a two-day meeting in London of top trade officials from Australia, Brazil, the European Union, India, Japan and the US.
With two months to go before an intermediate stage in the troubled four-year-old Doha round, an arrangement between the so-called Group of Six is widely regarded as essential if the 143 other WTO members are to follow.
Asked when and where the proposed summit might take place, Blair said: "We've obviously got to discuss with the other key people how this can be taken forward.
"But it's obviously got to be at the right moment to give the necessary push for the talks to succeed."
Blair set out a framework of sorts by recalling that George Bush's fast-track authority from Congress to negotiate international trade deals is set to expire next year.
Trade was the key political issue during Lula's visit, but was overshadowed by the continuing controversy into the circumstances of the shooting of an innocent Brazilian in the London subway in July by police who mistook him for a suicide bomber in the aftermath of the 7 July attacks.