President Dmitry Medvedev on Wednesday signed a decree banning supplies of S-300 missiles and other arms to Iran in a long-awaited move after weeks of deliberations by Russian officials.

"Dmitry Medvedev signed a decree 'on Measures to implement the United Nations Security Council resolution 1929 from June 9, 2010'," the Kremlin said in a statement.

The decree published on the Kremlin website forbids supplies of the S-300 air defence missiles to the Islamic republic, among other weapons.

Under the decree, supplies of any tanks, fighter jets, helicopters, ships and missile systems are forbidden.

Russia will also not supply Iran with any technologies related to ballistic missiles capable of delivering nuclear weapons. The decree also bans the transit of arms bound for Iran through Russian territory.

In addition, Iraninan citizens or companies will not be allowed to invest in any activities in Russia related to production of uranium.

An aide to Medvedev had told AFP in June that the S-300 missile deal would likely be scrapped, but that a formal decision would come in a decree.

The Kremlin made the decree public after the chief of the general staff Nikolai Makarov told Russian reporters Moscow had dropped plans to supply Tehran with the S-300s because they were subject to international sanctions.

"A decision has been taken not to supply the S-300 to Iran, they undoubtedly fall under sanctions," Makarov said in an apparent reference to the UN sanctions, the ITAR-TASS news agency reported.

"There was a decision by the leadership to stop the supply process, we are carrying it out," Makarov was quoted as saying.

Makarov however did not give a definite answer when asked whether the missile contract itself would be cancelled permanently.

"We will see, this will depend on Iran's behaviour," the Interfax news agency quoted Makarov as saying.

The decree would not mean a complete halt to all military cooperation between Moscow and Baghdad, Deputy Foreign Minister Sergey Ryabkov told Russian reporters in New York.

"We did not add anything to the list (of banned items), but on every point there we will have no further military cooperation with Iran. However, there are other forms (of military cooperation still allowed)," Ryabkov was quoted by RIA Novosti as saying.

The UN Security Council in June adopted a fourth round of sanctions against Iran over its nuclear drive, imposing broader military and financial restrictions on the Islamic republic.

Russia's support of the sanctions against Tehran and its failure to deliver air defence missiles has left Iranian leaders fuming over what they see as betrayal by a trusted ally.

Iran has over the past months been announcing steady advances in its nuclear programme, in defiance of international calls for it to freeze its sensitive uranium enrichment operations.

Russian Foreign Minister Sergei Lavrov said in June that UN sanctions would not affect the S-300 contract, as that the missiles were "defensive weapons" that did not fall under the terms of the sanctions.

Russia agreed the missile deal several years ago but has never delivered the weapons amid pressure from the United States and Israel, which fear they would dramatically improve Iran's defensive capabilities.

In June, Russian Prime Minister Vladimir Putin told French President Nicolas Sarkozy that Moscow would not sell the missiles to Iran in line with UN sanctions, a French official told reporters on condition of anonymity at the time.

Analysts praised what they said was much-needed clarification on the issue after months of deliberations and often contradictory statements by unidentified officials.

Russia's tougher line on Iran has coincided with a warming of its relations with the United States. Washington has repeatedly praised Moscow for its support in the nuclear crisis.

Makarov said he did not foresee any hurdles that could delay the ratification of a landmark Russia-US nuclear arms treaty signed earlier this year.

"The ratification may take place by the end of the year," he was quoted as saying.

The treaty -- signed by US President Barack Obama and Medvedev at an elaborate ceremony in Prague in April -- restricts each nation to a maximum of 1,550 deployed warheads, a cut of about 30 percent from a limit set in 2002.