* NATO tells Russia its missile shield poses no threat
* Rasmussen invites Russia to cooperate in shield
By Alexandra Hudson
BERLIN (Reuters) - A Kremlin threat to launch pre-emptive strikes on a planned NATO missile defense system in Europe is unjustified as the system poses no threat to Russia's security, the head of the Atlantic alliance said on Friday.
NATO has long insisted that the anti-missile shield it is developing is aimed at protecting member states from a possible Iranian attack, but Russia fears the system could undermine the effectiveness of its own nuclear arsenal.
In a stark escalation of rhetoric ahead of Vladimir Putin's return to the presidency next week, Russia's military chief-of-staff said on Thursday that Moscow might be forced to carry out pre-emptive strikes on NATO missile defense installations.
"These statements are unjustified," NATO Secretary General Anders Fogh Rasmussen said in Berlin after talks with German Chancellor Angela Merkel.
"Our missile defense system is not technically designed to threaten Russia in any way and we have provided that information to the Russians. Politically, we don't have any intention to attack Russia," he added.
NATO has invited Russia to cooperate on missile defense and they have shared defense interests, Rasmussen said, adding that NATO and Moscow had signed a pact 15 years ago pledging they would not use force against one another.
"The best way for the Russians to see with their own eyes that our system is not directed against them would be to co-operate actively," he said.
"We will continue our dialogue with Russia and I hope one day in the future we will reach an agreement."
General Nikolai Makarov, Russia's military chief-of-staff, told an international conference in Moscow on Thursday: "Decisions on the pre-emptive use of ... attack components will be taken in the period of heightening tension."
Testy exchanges between the Russian hosts and U.S. and NATO officials at the conference exposed how far apart the old Cold War foes remain on the terms of a deal that would allow them to cooperate on missile defense, an arrangement both say they want.
The missile defense system is due to be completed in four phases by about 2020 and includes interceptor missiles based in Poland and Romania.
Moscow says the West will gain the ability to shoot down Russian intercontinental ballistic missiles (ICBMs) in a few years, weakening Russia's nuclear deterrent.
Makarov said European states should decide whether protection against a possible future threat from nations such as Iran was worth the risk of facing down Russian weapons that would pose a "real threat" to countries hosting the facilities.
NATO will hold a summit in Chicago on May 20-21 at which the shield's first phase is to be declared up and running.
(Reporting by Alexandra Hudson; Editing by Andrew Osborn)