MOSCOW (AFP) - Russian Foreign Minister Sergei Lavrov and his US counterpart John Kerry will discuss the Ukraine crisis on the sidelines of a nuclear summit in The Hague next week, a Russian foreign ministry official said Saturday.

"A meeting between Lavrov and Kerry is planned on the sidelines of the summit in The Hague," to be held Monday and Tuesday, Interfax news agency quoted the official as saying.

The exact timing of the encounter was not immediately known.

Amid accusations that Russia was trying to splinter Europe in the Cold War-style struggle over the future of ex-Soviet Ukraine following the Kremlin's annexation of Crimea, Kerry said Thursday he would like to have another meeting with Lavrov next week in Europe.

A theme of this year's Nuclear Security Summit, first held in 2010 in Washington and again in Seoul in 2012, is preventing nuclear terrorism, according to the NSS website, but the event is in fact expected to be dominated by Moscow's annexation of Ukraine's peninsula.

US President Barack Obama has invited leaders of the Group of Seven (G7) industrialised countries and the European Union to a separate meeting to discuss the crisis.

G7 leaders from Britain, Canada, France, Germany, Italy, Japan and the United States will meet on Monday, diplomats have said, after the United States and the European Union tightened sanctions Thursday and Friday in response to the annexation.