Russia's foreign minister has blamed Gordon Brown's takeover as UK prime minister for a row about extradition.
Mr Lavrov said Russian extradition requests had gone unanswered
Sergei Lavrov told reporters that each new government needs "to find its own line" after assuming power.
But he added that he hoped common sense would prevail and that the situation was "moving in that direction".
Earlier, Russia said it will expel four UK embassy staff in the dispute about Moscow's refusal to extradite a suspect over Alexander Litvinenko's murder.
On Monday four Russian embassy staff were expelled from the UK and the visa facilitation process for Russian officials was suspended.
In retaliation, Russia said the four British embassy staff must leave the country within 10 days, and Moscow is to review visa applications for UK officials.
'Find its place'
Speaking during a press conference at the end of the Middle East Quartet's meeting in Lisbon, Mr Lavrov said it was up to Britain to determine how long the crisis would last.
He added: "We understand that when a new government comes to power in any country, it is seeking to find its place, so to say, seeking its own line.
KEY EVENTS IN CASE
1 November 2006: Alexander Litvinenko meets Andrei Lugovoi and another Russian at a London hotel
23 November 2006: Litvinenko dies in a London hospital
24 November 2006: A Litvinenko statement accuses Russian President Vladimir Putin of involvement in his death. Experts say Litvinenko was poisoned
6 December 2006: UK police say they are treating the death as murder
22 May 2007: Lugovoi should be charged with Litvinenko's murder, British prosecutors say
28 May 2007: UK makes formal request for Lugovoi's extradition from Russia
"Therefore, I can, to a large extent, see in what is happening also the factor of a new government."
Mr Lavrov condemned what he described as Britain's refusal to co-operate with Russian extradition requests, and said that Russia had responded immediately when the British authorities asked permission to send investigators to Moscow last December.
Similar Russian requests, he said, had gone unanswered for months.
Mr Lavrov said his government had still not seen "actual documents" relating to the Litvinenko affair and consequently did not know what had led the British authorities to regard Mr Lugovoi as a suspect.
Mr Litvinenko, an ex-KGB agent who had taken UK citizenship, died of exposure to radioactive polonium-210 in London in November 2006.
Traces of the radioactive isotope was found in several places visited by another former agent, Andrei Lugovoi, who denies involvement.
UK Foreign Secretary David Miliband said he was "disappointed" by Russia's decision to expel British Embassy staff - a move he called a "completely unjustified".
But Russian President Vladimir Putin said he thought both countries would overcome the "mini crisis".
Under the European Convention on Extradition 1957, Russia has the right to refuse the extradition of a citizen and its constitution expressly forbids extradition.
The UK has the right to request Mr Lugovoi be tried in Russia, but the UK's director of public prosecutions, Sir Ken Macdonald, has already turned down the offer.
The UK's director of public prosecutions has recommended Mr Lugovoi be tried for murder by "deliberate poisoning".