WASHINGTON — The Obama administration on Friday removed sanctions against three Russian organizations the US had previously accused of assisting Iran's effort to develop nuclear weapons.Penalties against a fourth Russian entity previously accused of illicit arms sales to Syria were also lifted.The timing of the decisions, published in Friday's Federal Register but not otherwise announced by the State Department, suggested the possibility of a link to US efforts to win Russian support for a new UN Security Council resolution expanding sanctions against Iran over its nuclear program.The State Department on Friday did not immediately respond to questions about lifting the sanctions.Two of the entities — Dmitri Mendeleyev University of Chemical Technology and the Moscow Aviation Institute — had been sanctioned in January 1999 under a 1994 executive order authorizing such action. The order was aimed at organizations determined to have contributed to a foreign country's development or production of weapons of mass destruction or missiles capable of launching such weapons.When the administration of former US president Bill Clinton announced those sanctions, then-Energy Secretary Bill Richardson said the two institutions "directly support Iranian efforts to develop nuclear weapons."At the time, the Russian government denied such support for Iran.US sanctions imposed in October 2008 against Russian state arms trader Rosoboronexport for alleged illicit assistance to Iran's nuclear program also were lifted by the State Department on Friday.Rosoboronexport said at the time that it had sold only defensive weaponry to Iran.Earlier this year, Anatoly Isaikin, head of Rosoboronexport, said Russia still considers Iran a valuable arms customer. That was a reassuring message to Tehran despite recent indications of Moscow's support for tougher Western sanctions.Isaikin told a news conference in late January that no international agreements bar Russia from selling weapons to Tehran.Russia signed a 2007 contract to sell the powerful S-300 air defense missiles to Tehran but so far has not delivered any. No reason has been given for the delay, but Israel and the United States strongly objected to Iran obtaining the long-range missiles, which would significantly boost the country's air defense capability.The State Department on Friday also lifted sanctions against Tula Instrument Design Bureau in April 1999 for providing anti-tank guided missiles to Syria.