KIEV -- The United States and other Western powers have welcomed Ukraine's decision to ratify the Nuclear Nonproliferation Treaty and to thus overcome a major stumbling block in relations between the former Soviet republic and the West and Russia.


The American ambassador to Ukraine, William Miller, described the decision as "a major step in the post-Cold War order" now emerging. Under the terms of the agreement, Ukraine should be nuclear free by the end of the century.


Miller said that Ukraine's decision to ratify the treaty "clears the way for strengthened relations between the United States and Ukraine." The Ukrainian president, Leonid Kuchma, is scheduled to leave for a trip to the United States on Saturday.


Some nationalist deputies in the parliament spoke out against ratification. "If we ratify the agreement we will become a banana republic. If we don't, people will take note of our president on the world stage," said Mikhail Ratushny.


Other deputies, however, pointed to economic incentives and political benefits to be gained from ratification. Failure to ratify the treaty has been one of the main obstacles in relations between Ukraine and the West. It has also been a point of friction in relations with Russia.


Commenting on the vote, Kuchma said that it was a decision "which corresponds not just to Ukraine's interests but to those of the world community." He told the parliament that a positive vote on the treaty would "show that Ukraine has no desire to blackmail the world community with nuclear weapons."


Security guarantees have proved to be the most complex issue surrounding Ukraine's decision to ratify the treaty. Foreign Minister Hennady Udovenko told the parliament that Ukraine has received notes from Britain, the United States and Russia assuring it of security guarantees. Udovenko said that the guarantees would be signed in the form of a memorandum at a meeting of the Council of Security and Cooperation in Europe in Budapest on Dec. 5 and 6. He also said that guarantees from France would be forthcoming.


In a last-minute condition attached to their ratification of the treaty, deputies voted to ask for upgraded guarantees, drawn up not in the form of a memorandum but as a legally binding international document. Miller said that he sees no difference between a memorandum and the document requested by Ukraine, but other diplomats have suggested the request may delay implementation of the treaty. The speaker of parliament, Olexander Moroz, has emphasized that the treaty "will only take effect once Ukraine has received guarantees of a normal legal character."


It appears, however, that after a long and delayed debate, the parliament has finally decided that it can no longer afford to risk lumbering the country with a reputation as a nuclear pariah state.


Kuchma told deputies that it would cost Ukraine up to $30 billion over the next 10 years if it wanted to keep the weapons -- a sum Ukraine is clearly in no position to afford.


On the eve of the vote, Russia threatened to suspend deliveries of nuclear fuel to Ukraine if it failed to ratify the treaty.


Some of the $700 million in aid already pledged to Ukraine by Western states to help with disarmament depends on the country's ratification of the treaty. Defense Minister Valery Shmarov, now visiting the United States, has said that Ukraine is bearing most of the cost of becoming nuclear free. Kuchma is expected to request more financial aid for the military during his negotiations with American leaders next week.


Last week Kuchma said that "the United States has played a great role in helping to resolve Ukraine's problems." He said that he hoped to attract American investment to Ukraine during his visit to New York and Washington. The decision by Ukraine's parliament to ratify the treaty might help make America's leaders more receptive to Ukraine's requests.