MOSCOW (AP) ― British Prime Minister David Cameron declared Monday that Russia and Britain must set aside bitter disputes over the poisoning death of a Kremlin critic in London five years ago to nurture new trading ties and help promote world stability in the wake of the Arab uprisings.

Cameron was in Moscow for the first visit to Russia’s capital by a British leader in six years, meeting with President Dmitry Medvedev, and holding the first talks by any British official with Prime Minister Vladimir Putin in more than four years.

Relations between Britain and Russia soured over the 2006 death of dissident ex-Russian security agent Alexander Litvinenko in London. Litvinenko made a deathbed statement accusing Putin of authorizing his killing. Russia has refused repeated British requests for the extradition of the chief suspect in the case, ex-KGB agent Andrei Lugovoi, who denies any involvement.

Following their talks, Medvedev said frosty relations between London and Moscow were thawing. But he warned Cameron there would be no change in Moscow’s refusal to hand over Lugovoi, and dismissed British claims that corruption within Russia’s legal system was discouraging foreign businesses from investing in the country.

“This will never happen, no matter what the circumstances,” Medvedev said on Britain’s hopes of putting Lugovoi on trial in the U.K. “We all have to learn to respect our legal frameworks.”

Putin, whose last contact with a British official was a brief 2007 phone call with then-British leader Gordon Brown, met with Cameron at his office and acknowledged the nations had a number of issues to overcome.

“Great Britain is our old trade and economic partner, and we have lots to discuss,” Putin said, greeting Cameron at the White House. Though Putin acknowledged Britain had been a major investor in Russia in the last 12 months, he said “investments in the real sector of the economy are rather modest.”

Foreign Secretary William Hague confirmed that Cameron had raised the Litvinenko case and other human rights concerns with Putin.

Cameron, who was joined on the visit by about 20 business leaders including oil company BP’s chief executive Bob Dudley and Royal Dutch Shell CEO Peter Voser, said he told Medvedev and Putin that their two nations would need to cooperate to grow their economies, despite differences.

BP has faced recurrent troubles in its commercial dealings in Russia. In a recent development, bailiffs last month searched the energy company’s Moscow office because of a minority shareholder’s lawsuit.

BP’s future in the country was among the subjects discussed by Cameron and Medvedev, an adviser to the Russian president told reporters.

“The president said that any issues arising in this sphere must be resolved within a legal framework. Executive authorities cannot interfere,” said Sergei Prikhodko, Medvedev’s foreign policy adviser.

Trade deals worth about 215 million pounds ($340 million) ― which could create 500 new jobs in Britain ― were signed during the visit, including plans for U.K. companies to work on Russian-led civil nuclear projects and assist in the redevelopment of Moscow’s Luzhniki Stadium.

Cameron insisted the Litvinenko case was not being ignored amid the push for trade, and disclosed that Hague had spoken to Litvinenko’s widow Marina before the British delegation traveled to Moscow.

“This issue hasn’t been parked, the fact is that the two governments don’t agree,” Cameron said at the Kremlin news conference alongside Medvedev. “I don’t think that means that we should freeze the entire relationship.”

In a speech at Moscow State University, Cameron said “the accused has a right to a fair trial. The victim and their family have a right to justice.”

Cameron later said intelligence cooperation between Britain and Russia would remain suspended as a result of Litvinenko’s killing.

Litvinenko’s friend Alex Goldfarb said the dissident’s widow was deeply disappointed that Cameron had decided to meet with Putin. “It is inconsistent to demand Lugovoi and at the same time shake hands with the man who has sent him on his mission in the first place,” Goldfarb said.

Lugovoi welcomed Cameron’s suggestion that the case should no longer hamper political and economic ties.

“For the first time in five years, I heard a calm reaction from a high-ranked British official to the Litvinenko case,” Lugovoi said, the ITAR-Tass news agency reported.