By urging Congress this week to let Puerto Rico vote to become America's 51st state, President Bush is trying to breathe new life into an old issue. But it's an issue that would be better left alone.

In fairness to Bush, the position he took this week on Puerto Rico's future simply echoed statements he has been making since at least 1981. Moreover, he is in good company in doing so. Other presidents have favored statehood for Puerto Rico. So did a 1977 presidential commission, which studied the issue at length.But the fact remains that Puerto Ricans have considered and rejected statehood at least twice since 1967. There's no reason to think public sentiment has changed much, if at all. Even if it did change, the obstacles to statehood are formidable.

By law, the text of the statehood plan would have to be approved by two-thirds of both houses of the Puerto Rican legislature. But Puerto Rican law also prevents any one political party from gaining a two-thirds majority. Currently, the island's three main parties are divided on its future, supporting either statehood, independence, or continued status as a commonwealth.

If these obstacles could be surmounted, Puerto Rico would not fit in well with the rest of America. Unemployment there is three times as high as it is throughout the United States. Per capita income is only about half that of the poorest American state, Mississippi. More than half of its families have incomes below the federally-defined poverty level.

Then there are the language problems. Spanish is the language of Puerto Rico, English the language of America. If Puerto Rico became a state, the U.S. could find itself with multi-language conflicts like those of Canada, Belgium, and other countries.

From Puerto Rico's point of view, many of its people are afraid of losing their separate identity if they are swallowed by the American union. Others fear that industry would hesitate to locate there without some of the financial breaks that come with commonwealth status. This status means that Puerto Ricans are U.S. citizens, with unrestricted access to the mainland United States. But they are not subject to federal taxes and do not vote in presidential elections. They are represented in Congress by a single, commissioner who can vote only in committees.

The time may come when statehood will be appropriate for Puerto Rico. But that time still seems a long way off.