THE CLINTON administration is trying, for the third consecutive year, to wring money out of Congress to pay the United States' debts to the United Nations. In principle, this should not be difficult. The Senate has voted overwhelmingly in favor of repayment, provided that the United Nations reform itself. A majority in the House would be happy to go along with that. But Rep. Chris Smith (R-N.J.) is determined to link the U.N. money to an antiabortion policy that President Clinton would veto.

For the past two years, this linkage has blocked the U.N. money. Unless the Republican House leadership can prevail upon Mr. Smith to back off this time, there may be another blockage, and a deadbeat United States may lose its vote at the United Nations. That would put it in the same category as Iraq and Togo.

This year, even more than in the past, there are excellent reasons for the House leadership to rein in Mr. Smith. The United States has a new ambassador to the United Nations, Richard Holbrooke, who is determined to make the United Nations an effective instrument for serving U.S. interests. Mr. Holbrooke has already insisted that the United States get back a seat on the U.N. budget committee that it had earlier lost because of its indebtedness. He is committed to forcing through the U.N. reforms that the Senate demands, including a reduction in the United States' share of the organization's budget.

At the same time, the United Nations has recently taken on several jobs that the United States wants done but does not want to do itself. It has sent, or is about to send, peacekeepers to Kosovo, East Timor and Sierra Leone. All three ventures are tough and could go badly wrong if they are underfunded. Other countries are paying their part. The United States, by contrast, has voted in favor of these missions but fails to pay what it owes to the institution that is running them. It is easy to understand why other countries resent American power when it is exercised so capriciously.

Moreover, Mr. Smith is not only damaging the United Nations; he is advancing his antiabortion cause in a manner that even pro-life advocates ought to find troubling. The language that he seeks to attach to U.N. dues would prevent any family planning organization that receives U.S. aid from "advocating" abortion. The definition of advocacy might include organizing a conference at which abortion is discussed or printing literature that others could use in debates on abortion. These conditions constitute a gag on family planning organizations working in the developing world. That kind of suppression of free speech would be unacceptable at home. It should not become part of U.S. foreign policy.

Mr. Smith is wrong on the United Nations, wrong on family planning and wrong to link these two unrelated subjects. Earlier this year, Mr. Smith lost a battle to include his antiabortion language in the foreign appropriations bill, whereas a more moderate amendment passed the House. But he nonetheless declares that he will thrust his policy into other bills. The question is whether the House leadership has the guts to stop him.