US Secretary of State Hillary Clinton called Thursday on NATO to press Russia to match any future move by Washington to reduce its estimated 240 tactical nuclear weapons in Europe.

In a dinner speech to fellow NATO members in Tallinn, the capital of the former Soviet state of Estonia, she also urged the alliance to embrace missile defence as an integral part of NATO's deterrence against new threats.

In the post Cold War era, these perceived threats from nuclear and other weapons of mass destruction, US officials say, come no longer from Russia but from states like Iran and Islamist militant groups like Al-Qaeda.

"In any future reductions, our aim should be to seek Russian agreement to increase transparency on non-strategic nuclear weapons in Europe, (and) relocate these weapons away from the territory of NATO members," Clinton said.

The chief US diplomat appeared to rule out early withdrawal of an estimated 240 US nuclear weapons stored in NATO nations Belgium, Germany, Italy, the Netherlands and Turkey -- weapons that would be carried by bomber aircraft.

Russia is thought to have at least four times as many such arms.

In her remarks to foreign ministers of the 27 other North Atlantic Treaty Organization members, Clinton spelled out more explicitly than before US plans for how future reductions of nuclear weapons should take place.

Aides gave journalists her prepared remarks which were given behind closed doors.

President Barack Obama had hinted at such an approach in his "Nuclear Posture Review," unveiled on April 6. Russia and the United States last month sealed a landmark deal to reduce long-range strategic nuclear weapons.

Speaking at a press conference earlier in Tallinn, NATO Secretary General Anders Fogh Rasmussen heralded Clinton's own appeal.

"I do believe the presence of American nuclear weapons in Europe is an essential part of a credible deterrent," Rasmussen told reporters.

The appeal was likely to stir resistance from not only Russia but some members of the alliance, including Germany, which want the United States to reduce the tactical nuclear weapons without linking them to Russian moves.

Germany appeared impatient for cuts in US tactical nuclear weapons.

"It's time to make progress on disarmament. That includes on nuclear weapons," German Foreign Minister Guido Westerwelle said in Tallinn, Estonia's capital.

"We must take advantage of this window of opportunity for disarmament," he added.

Belgium, Luxembourg, the Netherlands and Norway are also keen for the arms to go.

A senior US official underlined the need to stand unified over the issue.

"Our principle, and most important guidepost for moving into this discussion is that we don't want to divide the alliance on this issue," he said.

The debate has deep resonance for Estonia, which joined NATO in 2004 and like fellow ex-communist alliance members puts some stock in a nuclear buffer amid concerns about its resurgent Cold War-era master Russia.

"Nuclear deterrence based in Europe must remain, as it preserves close trans-Atlantic ties and allows for greater flexibility in deterrence," Estonian Foreign Minister Urmas Paet said as the meeting opened.

The Obama administration will also press NATO for "communique language" at a summit in Lisbon in November "that establishes missile defence as a NATO mission," Clinton said.

"Missile defence is part of our broader efforts to combat the danger posed by weapons of mass destruction and their delivery systems," she said.

The United States had already stirred unease in the Kremlin over its previous plans to deploy a missile shield in Poland and the Czech Republic, two former Soviet satellite states.

The system has since been scaled down, but NATO officials say the aim has never been to point it at Russia, and even urdged Moscow to participate in it.