Foreign technology has developed so rapidly in the last 10 years that the Europeans and Japanese now threaten the American dominance of space for the first time since the dawning of the Space Age 25 years ago, according to a report to Congress yesterday by its Office of Technology Assessment.

OTA said the United States is on the brink of losing its space leadership role to foreign competition in satellite communications, the remote sensing of the Earth's resources from space and in the manufacture of exotic metals and pharmaceuticals in space. OTA warned that the American space shuttle even faces competition from the European Space Agency's Ariane rocket launcher in the years directly ahead.

"International competition in space applications is a reality," the 382-page report on civilian space policy said. "The Europeans and Japanese have targeted specific space technologies for development, and they will soon be providing stiff competition for services heretofore offered only by the United States."

The stiffest and most far-reaching challenge to U.S. space technology, the OTA said, is coming in space communications, an area dominated by the United States since the launching of the Telstar communications satellite in 1962. The civilian space agency began to take itself out of satellite communications research under pressure from private industry in 1973, OTA said, leaving a gap that was quickly filled by the Europeans and Japanese.

"As a result, many of the new developments in satellite communication have come from the Europeans and Japanese," the OTA said. "In some areas, they seem to have leapfrogged U.S. technology."

OTA said the Japanese have already become the world's leading supplier of earth stations for countries plugged into the INTELSAT communications satellites and are likely to take the world market lead for earth stations to receive direct broadcasts of television from space.

OTA also pointed out that an Italian firm named Telespazio plans to be the first to market a broad-band radio communications system that will be able to handle hundreds of times as many telephone calls as today's systems do.

"To allow ourselves to fall into second place in an important area of space applications (as the radio system) would be to ignore a basic tenet of U.S. space policy," the OTA said. "That is, that the U.S. will maintain a position of leadership."

The OTA also pointed out that the United States will launch its last Landsat satellite to explore the Earth's natural resources next month, which is about the time that France will begin to advertise a Landsat-type satellite to be launched in 1984 for commercial users in all countries.