Authors: By DAVID STRINGER
MOSCOW (AP) -- British Prime Minister David Cameron insisted Monday that Russia and Britain can overcome the sharp differences in their relations - even the 2006 poisoning death of a Kremlin critic in London - to seal 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.
Ties between Britain and Russia soured over the 2006 poisoning 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 British requests for the extradition of the chief suspect in the case, ex-KGB agent Andrei Lugovoi, who denies involvement.
Following talks at the Kremlin, Medvedev told Cameron there was no prospect of Lugovoi facing a British court because the Russian constitution prohibits the extradition of a Russian citizen.
"This will never happen, no matter what the circumstances," Medvedev said during a news conference with Cameron. "We all have to learn to respect our legal frameworks."
The two leaders also joked about what Cameron believes was a KGB attempt to recruit him during a 1985 trip to Russia when he was still a teenager.
"I'm sure that David would have been a very good KGB agent, but in that case he would never have become prime minister of Britain," Medvedev said at the news conference.
Cameron, who was to meet with Putin later in the day, said his visit would focus on developing new businesses opportunities.
Since taking office in May 2010, Cameron has looked to developing economies to help kick-start Britain's sluggish growth, leading large delegations of business executives on visits to India and China.
"I accept that Britain and Russia have had a difficult relationship for some time," Cameron told students Monday morning at Moscow State University. "We should be candid about the areas where we still disagree. But I want to make the case for a new approach based on cooperation."
Cameron was accompanied by about 20 business leaders, including oil company BP's chief executive Bob Dudley and Royal Dutch Shell CEO Peter Voser, and planned to seal new deals worth 215 million pounds ($340 million) - which would create 500 new jobs in Britain.
British companies are also likely to win new rights to bid for contracts on Russian-led civil nuclear projects, while Cameron's government will support Russia's efforts to join the World Trade Organization.
"Never believe that just because the relationship is difficult now, it can't be better in the future," Cameron said in response to a student's question. "There are many reasons for optimism and hope."
In an interview with Britain's Sky News television, Lugovoi urged Britain to focus on trade, and accept that demands for him to face trial were unlikely to be met.
"I am sure that this is the dream of Cameron - don't speak about me. It looks idiotic," Lugovoi said. "For the last four years, the first question from every British politician has been about me, despite the fact that Britain is the biggest investor in the Russian economy."
Cameron insisted the Litvinenko case was not being ignored amid the push for trade, and disclosed that Foreign Secretary William Hague had spoken to Litvinenko's widow Marina before he and the British leader 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. "I don't think that means that we should freeze the entire relationship."
But Cameron warned that a major upgrade of trading ties would need Russia to make progress on reforming its criminal justice system.
Last month, BP complained that a Moscow office had been illegally raided after Russian bailiffs accompanied by armed policemen searched its premises in connection with a lawsuit.
Foreign businesses "need to know that they can go to a court confident that a contract will be enforced objectively and that their assets and premises won't be unlawfully taken away from them," Cameron said.
Hinting at the Litvinenko case, Cameron called on Russia to do more to ensure its courts were impartial.
"The accused has a right to a fair trial. The victim and their family have a right to justice," Cameron said in his speech. "There are extradition cases Russia wants to pursue, and we still disagree with you over the Litvinenko case."
Britain ended intelligence cooperation with Russia as a result of Litvinenko's killing. Cameron confirmed that it would not be restored, but said law enforcement officials may work more closely against organized crime. Cameron also claimed that Moscow and London could work together to tackle the threat of terrorism - and must continue to show unity on efforts to prevent Iran from developing nuclear weapons.
Cameron also urged Russia to work closely with Britain and other United Nations Security Council members to help ensure stability in the Middle East and North Africa.
Russia has so far refused to support efforts by Britain, the United States and France to pass a U.N. resolution authorizing sanctions against the regime of Syrian President Bashar Assad.
Hague said talks Monday would focus on efforts aimed at persuading Russia to support a tougher U.N. stance on Syria.
"The stability of corrupt and violently repressive dictatorships in Middle Eastern states like Gadhafi's in Libya is false stability," Cameron said.
"The transition to democracy may well have its difficulties and dangers, but it is the best long term path to peaceful progress and is a powerful alternative to the poisonous narrative of Islamist extremism," he said.
Dudley joined the trip following the collapse earlier this year of BP's planned Arctic oil deal with Russian state-owned energy company Rosneft - an agreement that had been seen as critical to BP's recovery from the Gulf of Mexico spill.
Rosneft last month agreed to a partnership with U.S. company Exxon Mobil to develop offshore oil fields in the Russian Arctic, one of the world's last regions with major untapped hydrocarbon deposits. In return, Rosneft has the option to acquire parts of oil projects in Texas and the Gulf of Mexico.