American astronauts and Russian cosmonauts shared earthly concerns Tuesday at the opening of a congress of space explorers devoted to protecting the planets' ecology.


The 10th congress of the Association of Space Explorers opened on Red Square, where a giant bell-shaped balloon floated between the graceful, colorful onion domes of St. Basil's Cathedral and the Kremlin's Spassky Tower.


"I'm very happy to be here in Moscow," said Tom Stafford, the first astronaut to participate in the joint U.S.-Soviet Apollo-Soyuz program of the 1970s. Stafford delivered his brief remarks in Russian.


President Boris Yeltsin sent his congratulations to the congress, saying in a message that space veterans could contribute to international space endeavors and worldwide efforts to resolve ecological problems.


"The future of the Earth wholly depends on joint efforts by all the countries and people aimed at environmental protection, including the wide possibilities offered by manned spacecraft," Yeltsin said.


Participants stressed the importance of space cooperation now that the space race has ended.


"We come to celebrate this brotherhood among those who have flown in space," said astronaut John Fabian, who serves as co-chairman of the association.