Russia said Saturday it may be ready to drop its objections to the US-backed missile defence shield for Europe if it receives a formal security pledge from the United States.

The comments by Foreign Minister Sergei Lavrov suggest an easing of Moscow's position and precede a meeting between US President Barack Obama and his Russian counterpart on the sidelines of G8 summit in France next week.

Lavrov said during talks with the German and Polish foreign ministers that missile defence negotiations with the United States and NATO were "progressing but slowly."

"We are proposing, and asking for it to be put in writing, that the missile defence system for Europe is not directed against any of the participating states -- not NATO, Russia or other European states," Lavrov said.

"We are told there is no need to get this down in writing because this is inherently the case," he told a televised news conference.

"But if it is inherently not aimed against Russia, why not write (that) down?" he asked.

Lavrov's nuanced language appears aimed at easing tensions between Washington and Moscow on the eve of the Group of Eight (G8) summit talks next Thursday and Friday.

Russia has previously sought veto power in the system's operation -- a subject not broached by Lavrov.

President Dmitry Medvedev used a closely watch pre-election television appearance this week to warn the United States of a return to the Cold War should the shield be constructed despite Russia's objections.

And the chief of the military's general staff warned Friday that the shield's deployment could lead to a "mad arms race".

Russia's tough talk and decision to test two heavy nuclear missiles in the past month underscore a fear in Moscow that the Obama administration is paying lip service to the "reset" in relations announced by Washington in 2009.

The United States argues that the shield is meant only to protect Europe from nations such as Iran but has said nothing about Russian security safeguards.

Analysts note that Moscow is primarily worried the system will leave a permanent stamp on the security map of Europe and formalise the reduced role Russia plays in the post-Cold War world.

The shield could theoretically be expanded to sizes that one day neutralise Russia's shrinking nuclear arsenal, or transformed into an offensive weapon that target its soil.

"This issue is so serious that we cannot ignore a single detail," Lavrov said.

But he stressed that Moscow saw itself joining the systems under the right conditions.

Russia envisioned "a joint concept and architecture of a future European missile defence system," Lavrov said.

"We hope that we will be able to resolve these issues -- at least at the expert level."