Russia and the United States will continue to discuss missile defence independent of their planned signing of a landmark nuclear arms treaty in Prague next week, a senior Kremlin official said Friday.

"The presidents of Russia and the United States agreed from the start that the subject of the new treaty will be strategic offensive weapons," said Sergei Prikhodko, foreign policy advisor to President Dmitry Medvedev.

"Missile defence is a subject of dialogue between our countries in a different format," the Interfax news agency quoted Prikhodko as telling Russian reporters.

Medvedev and his US counterpart, Barack Obama, are due to sign a nuclear disarmament pact to succeed the 1991 Strategic Arms Reduction Treaty in Prague on April 8.

US plans to set up missile defence systems in eastern Europe have run into categorical opposition from the Kremlin which says they represent a direct threat to Russia.

Prikhodko said the new treaty would explicitly acknowledge the strategic link between offensive and defensive systems -- a link Moscow has long insisted upon -- and said it would have "legally-binding status," Interfax said.

Top officials from both countries however have acknowledged that the new treaty would not formally prevent either side from unilateral deployment of missile defences.

Signed in 1991, START led to huge reductions in the Russian and US nuclear arsenals and imposed verification measures to build trust between the two former Cold War foes.

Prikhodko reiterated Russia's threat that Moscow would reserve the right to abandon the treaty in case Russia felt Washington's anti-missile defence threatened its national interests.

"This position covers a quantitative and qualitative build-up of the US strategic anti-missile defence potential," Interfax quoted Prikhodko as saying.

He added Russia's position on the US missile plans would be stipulated in an addendum to the 160-page treaty, which he called an "independent political document" and that Washington may have a similar supplement.

Under the new agreement, US monitors will no longer be permanently based in the town of Votkinsk, where Russia manufactures its strategic missiles, Prikhodko added, ITAR-TASS reported.

He also said that Medvedev will travel on an official visit to the United States this year, state news agency RIA Novosti reported, without providing any specific dates.

Last July, Obama visited Moscow for a bilateral summit where the two leaders agreed on a major "reset" of ties, including the signing of the START successor treaty.