After lengthy negotiations and months of diplomatic pressure from the United States, Ukraine agreed Friday to new controls over the export of weapons technology and canceled a proposed deal for nuclear cooperation with Iran.

Ukrainian Foreign Minister Hennadiy Udovenko announced the agreement after talks with Secretary of State Madeleine Albright, who was on the first leg of a seven-country tour.At a news conference in the ornate Mariinsskiy Palace, Albright hailed Ukraine's decision, saying it will cement the country's place in the international effort to halt the spread of weapons of mass destruction.

Udovenko also disclosed that Ukraine is planning to become a member of an international agreement designed to curb the spread of missile technology. Albright pledged support for Ukraine's immediate membership.

Ukraine's decision to cooperate on export controls is significant because, as a major cog in the military apparatus of the former Soviet Union, it is in a position to engage in weapons proliferation on a large scale.

The Clinton administration has been deeply concerned about a Ukrainian plan to go ahead with a Russian purchase of an estimated $45 million in turbines for two Russian-designed nuclear reactors in Iran.

Despite Iranian pledges to allow international inspection of the facilities, the Clinton administration is convinced the project is part of an Iranian nuclear weapons program.

Since Ukraine achieved independence from the Soviet Union six years ago, the United States has eagerly courted the strategically located country with vast expanses of fertile land and 52 million people. More than $3 billion in American assistance has been earmarked for Ukraine since independence.

Udovenko said the decision to halt nuclear cooperation with Iran was not easy because of the "substantial financial losses" Ukranian companies will suffer.

Ukrainian President Leonid Kuchma, who led his government's delegation to the talks with Albright, said Russia has the capacity to build the turbines for the Iranian nuclear project.

As a result of Ukraine's decision to join the 29-nation Missile Technology Control Regime, the United States and Ukraine will be able to expand space cooperation.

The Clinton administration has limited such cooperation until now because space-launch and ballistic missile technologies are essentially interchangeable.

Also, Ukraine's pledge to tighten export controls opens the way for Westinghouse Electric Corp. to bid on a $1.2 billion project to complete two Russian-designed nuclear plants in Ukraine.