WITH the clock ticking, United States officials are scrambling to round up enough votes to guarantee the longevity of a treaty that for 25 years has helped contain the global spread of nuclear weapons.
The 172 signers of the 1968 Nuclear Non-Proliferation Treaty (NPT) will meet in New York starting April 12 to decide whether to extend the NPT permanently, as the United States wishes, or temporarily, as some nonnuclear states prefer.
''We're reasonably optimistic that we will come out of the review conference with a majority in favor of a permanent extension,'' says Lynn Davis, Undersecretary of State for Arms Control and International Security Affairs. ''But we're not so assured of that that we're not in a full-court press.''
The NPT commits states that do not have nuclear weapons not to acquire them. It commits states that do have them to a gradual build-down, leading to the eventual abolition of nuclear weapons.
The State Department estimates that between 60 and 70 countries now favor a permanent extension, short of the 86 needed for final approval. Unofficial estimates run as high as 75 in favor.
US officials have seized every opportunity -- including the recent United Nations ''Social Summit'' in Copenhagen -- to lobby officials from undecided states.
Their efforts are focused on six key nonaligned countries -- Mexico, Colombia, Indonesia, Egypt, South Africa, and Nigeria -- all of which are now counted as ''undecided'' or ''leaning toward.''
African states key
One of the administration's biggest hopes is South Africa, which voluntarily gave up its arsenal of six nuclear bombs and in 1991 signed the NPT. If the Pretoria government agrees to a permanent extension, other African nations might be persuaded to go along.
The administration's biggest concern is Egypt, which has demanded that Israel -- one of three undeclared nuclear states -- commit to sign the NPT as the price of its vote for a permanent extension. Egypt has lobbied other Arab nations to follow suit.
Egyptian Foreign Minister Amr Moussa has led Egypt's campaign on the NPT. During a recent visit to Washington, he was told by US officials that Israel would not sign the NPT before the conclusion of a comprehensive Middle East peace and while Iran, Iraq, and Libya continue to harbor nuclear ambitions.
''Moussa and other Egyptians have heard this from enough people that it's beginning to sink in,'' says another senior State Department official.
Following a meeting last week in Egypt with visiting US Secretary of State Warren Christopher, Egyptian President Hosni Mubarak hinted that compromise was possible. One possible face-saving formula: a statement by Israel that in the context of peace in the Middle East it would cooperate in efforts to free the region of weapons of mass destruction.
The next test of Egypt's intentions will be a meeting of Arab foreign ministers in Cairo on March 22.
The NPT issue will be on Vice President Al Gore's agenda when he travels to the region between March 19 and March 24 and meets with, among others, Mr. Mubarak.
Some nonnuclear states resent the nuclear weapons monopoly the NPT gives to five states: the US, France, Britain, China, and Russia. Many favor a series of 25-year extensions because a permanent extension would take pressure off the five to live up to their agreement to disarm.
The big five
The five will go into the conference without the benefit of two tokens of their good intentions to eventually get rid of their nuclear weapons.
A comprehensive test-ban agreement among the five, which could lead to the end of nuclear testing by 1996, is ''reasonably close,'' according to another senior State Department official, but must await the results of the second round of French national elections, May 7. The review conference ends on May 12.
The START II, which would slash US and Russian nuclear arsenals, will probably be ratified by the US Senate, but not the Russian parliament, before the conclusion of the NPT review conference.
Permanent extension of the NPT is a high priority for President Clinton, who by phone or mail has personally lobbied a number of foreign leaders on the issue.
Most observers believe the US will get its desired majority. After that threshold is crossed, US officials hope, there will be a snowball effect leading to an overwhelming vote in New York in favor of permanent extension.
Outside experts caution that if the US overplays its hand or gives any indication that it is satisfied with a technical majority based largely on Western votes, some nonnuclear states might vote against a permanent extension at the review conference or by withdrawing from the treaty.
''If you win a bare majority and the losers go away mad, there could be defections after the review conference,'' says George Bunn, a consulting professor at Stanford who helped negotiate the NPT.