LONDON — REPRESENTATIVES of the seven leading industrialized nations met yesterday in London to reassess their position on aid to the Soviet Union in the wake of the failed coup and the resulting crisis.The officials were called to London by British Prime Minister John Major, chairman of the Group of Seven (G-7) nations, to agree on a joint economic policy before he visits Moscow this weekend for talks with Soviet leaders. They were to decide whether decisions made regarding the Soviet Union at last month's G-7 London summit remain valid, said a spokesman for the Ministry of the Treasury. The G-7 then agreed to offer technical assistance to the Soviet Union but rejected Soviet President Mikhail Gorbachev's pleas for billions of dollars in direct aid. The leaders also pledged to help the Soviet Union's integration into the world economy by giving it special status in the International Monetary Fund. The officials will discuss whether to offer immediate economic aid or seek greater guarantees of stringent economic reforms and defense cuts before considering such a step. Speaking on television in the United States, where he is visiting President Bush, Mr. Major said the G-7 must help Soviet moves toward a market economy but stressed a clear economic plan must be put in place immediately. Previously tentative moves toward a market economy have raced ahead since the coup failed, also spurring the breakaway of Soviet republics. Besides Britain, the G-7 is composed of the United States, Canada, Germany, France, Japan, and Italy.