MOSCOW (AP) _ The Soviet Union on Friday accused the United States of violating the 1972 Anti-Ballistic Missile treaty by putting into operation an upgraded radar facility in Greenland.

A Foreign Ministry statement said the Soviet Union ''insists that the United States take, without delay, measures to rectify the violation of the ABM treaty.'' It described the deployment of the Thule, Greenland radar station as ''unlawful.''

The statement also accused the United States of mounting a campaign against a Soviet radar facility to divert attention from the Greenland issue.

It was distributed by the Tass news agency and read on Soviet television.

The Pentagon confirmed in a statement Friday that the Thule station returned to operation Thursday after being upgraded.

''The facility ... predates the ABM treaty,'' the Pentagon statement said. ''Studies of that treaty by this administration and the Carter administration have shown that modernizing these early warning facilities is fully consistent with all of the provisions of the treaty.'' Under traditional interpretations, the ABM treaty signed by the United States and Soviet Union bans the testing and deployment of space-based defenses against nuclear missiles and limits land-based systems.

A broader reading, called the 'legally correct interpretation'' by the Reagan administration, is that such systems can be developed and tested if based on technology not understood in 1972.

''The Soviet side is seriously concerned over the fact that the radar set up in Greenland and one planned to be set up in Britain ... have characteristics allowing them to cope with the tasks of warning against a missile attack, and potentially with the tasks of anti-ballistic missile defense,'' the Soviet statement said.

The British station is in Fylingdales Moor and is being upgraded in the same manner as the Thule station.

The Soviets said the ABM treaty limits deployment of new radar with such capabilities. They also have said President Reagan's Strategic Defense Initiative project, or ''Star Wars'' space-based defense system, violates the treaty.

''The 'argument' put forward by Washington that it is allegedly only modernizing the (Greenland) station that already existed there is groundless,'' the statement said.

The Soviets raised the issue two days after Soviet leader Mikhail S. Gorbachev said he would agree to the worldwide elimination of Soviet medium- and shorter-range missiles if the United States did the same.

The Soviet statement also accused the United States of campaigning to stop a Soviet radar facility in Krasnoyarsk, in central Siberia, to detract attention from the Greenland facility.

It said the Krasnoyarsk facility will be used only to track space vehicles and will not fall under the ABM treaty. It added that the Soviets are willing to mothball the Krasnoyarsk radar to prevent it from becoming a problem.

The U.S. has said the facility will violate the ABM treaty.