WHEN Fidel Castro Ruz made his last visit to the United Nations, he was the object of a rare consensus in Washington. The only way to deal with his threatening, Soviet-backed regime, Republicans and Democrats agreed, was to isolate and strangle it.
Sixteen years later - with another UN visit in the offing - the consensus has evaporated. With the Cuban leader weakened and vulnerable, politicians now debate whether tightening or relaxing economic sanctions will bring his rule to the quickest end.
"There are two philosophical roads you can go down: The best way to undermine Castro is either to ease up on the sanctions and flood Cuba with capital or to deny Castro hard currency," says a congressional source. "After that, you're debating tactics."
At this writing, Mr. Castro had not yet been granted a visa to attend 50th anniversary celebrations at the UN later this month.
Conservative lawmakers oppose giving him a visa on the grounds that he is a sponsor of terrorism and will use his trip to lobby against continued United States economic sanctions.
A senior administration official responds that under the agreement establishing UN headquarters in the US, "it would be hard to imagine denying a visa to a head of state."
The White House and Congress agree that with the Soviet Union gone and communism in disrepute, Castro is living on borrowed political time. The question is how to shorten it.
Anti-Castro hawks in Congress, including Senate Foreign Relations Committee chairman Jesse Helms (R) of North Carolina, say the US should tighten its sanctions, imposed in 1962, to finish off Castro's regime.
Many US businessmen reply that unilateral sanctions haven't worked. They advocate loosening the embargo to allow US firms to compete for business in Cuba.
PRESIDENT Clinton has a foot in both camps. He urges maintaining sanctions but also opening Cuba wider to the contagious idea of democracy.
The debate was stirred again last Friday when Mr. Clinton announced that he would permit US news organizations to establish bureaus in Cuba and allow Cuban journalists to work in the US. A presidential executive order also eases …