Soviet President Mikhail Gorbachev, in a letter appealing for help from the leaders of the major industrial democracies at this week's Houston summit, was far more urgent and specific about his needs than he was in a similar letter last year, according to text of the document.

"At this time the USSR is going through an extremely critical stage of perestroika," Gorbachev said in the letter addressed to President Bush as the host of the summit.

Gorbachev also acknowledged that he was trying to break down "obsolete economic structures" in the Soviet Union. "Without these radical steps, a further renewal of our society will be impossible," he said. The Soviet president made a series of requests that encompass the range of help now being considered -- and in some cases offered -- by western nations: credit, investment and technical expertise.

By contrast, last year, when Gorbachev wrote western leaders as they met in Paris, Soviet officials then said direct Western assistance was unneeded and unwanted. Instead, Gorbachev asked for cooperation, saying his perestroika reform program was "aimed at full and complete participation in the world economy."

This year's letter was shared by Bush with the leaders in Houston, but not made public. Sources made the text available to The Washington Post.

The letter, dated July 4, reflects what many U.S. and European specialists call a growing sense of urgency in Moscow's appeals. Although Gorbachev prevailed at the Communist Party Congress, the sources said the Soviet president still needs to demonstrate progress on the economic front in the near term.

"He wants to be able to show something soon," said a senior U.S. official. "He has demonstrated he can manipulate the levers of power, but the levers don't pay off as they once did in the way the country functions. He is looking to aid as a way to demonstrate some signs of success."

In his letter, Gorbachev thanked the western leaders for steps already taken to help Moscow. He said "in retrospect" over the last year, "We are of the opinion that the Soviet leadership has done everything in its power to support its new policies with concrete actions at home and abroad."

Gorbachev observed that "disaramament succeeds more and more," and said "overcoming the economic division of the world is now the order of the day."

"At this time, the Soviet leadership is looking for new possibilities to supplement the internal transformations through financial and economic support from outside," Gorbachev said. He appealed for credit, "the luring of foreign capital," transfer of management expertise and other measures "which will serve for the establishment of a competitive-oriented economy."

While the "first contacts" have taken place "and we are beginning to find understanding," Gorbachev said, "Perhaps it would be possible to talk about working out long-term agreement on large-scale credit and cooperation over investments, which would be a serious factor to stabilization and transition to the market economy," he said.

In Houston, after a debate over direct Soviet aid, the western leaders ordered a six-month study of Soviet needs. Bush has said the United States will not provide direct aid until Moscow meets a series of political conditions.

Historically plagued by inefficiency and consumer goods shortages, the Soviet economy has been plunged into even more difficulty as Gorbachev has struggled to make the transition to a market economy. A senior Japanse official told reporters in Houston that Soviet economic growth is now dropping 5 percent a year, the equivalent of a severe recession. Soviet officials have recently acknowledged difficulty in repaying foreign debts.