John Kerry Sergei Lavrov
Kerry Lavrov have met numerous times since the Ukraine crisis erupted but not in MoscowReuters

The United States and Russia are discussing a possible visit to Russia by a top diplomat for talks on the Ukraine crisis.

US secretary of state John Kerry could visit Moscow for the first time since the crisis erupted at the start of last year in eastern Ukraine.

Diplomatic ties between the US and Russia have become increasingly strained to their worst level since the end of the Cold War.

The prospect of Kerry attending Russia comes as the conflict in eastern Ukraine has escalated in recent weeks.

"Talks [on a possible Kerry visit] have been going on for weeks," said a diplomatic source, as quoted by Reuters news agency.

Russian newspaper Kommersant reported that the American Secretary of State would meet with his Russian counterpart Sergei Lavrov on February 4, although there has been no confirmation regarding dates.

The United States and the European Union have imposed sanctions on Russia after it annexed the Crimea peninsula from Ukraine. The allies have also accused Russia of fuelling the conflict in eastern Ukraine, which has reignited in the past month.

More than 5,000 people have been killed in the fighting between pro-Russian separatists and Ukrainian government forces, according to UN figures.

The separatist rebels recently seized the Donetsk airport and launched an assault on the port city of Mariupol, shattering a fragile ceasefire in the process.