Specialists on nuclear energy from East and West agreed here today to open negotiations on an international system for early notification of nuclear accidents and coordinated assistance in the event they occur.

The agreement came at an emergency meeting of the International Atomic Energy Agency's board, called by West Germany following the Chernobyl accident in the Ukraine.

Attending officials said that the agreement reached by the IAEA eventually could result in far-reaching changes in the present system of international controls on nuclear power. The meeting, attended by representatives of 35 nations, including the Soviet Union and the United States, was called to discuss the Chernobyl accident and its aftermath.

A statement after today's meeting called for the negotiation of an international agreement that would commit signatory countries "to provide early notification and comprehensive information about nuclear accidents with possible trans-boundary effects." It urged a second accord permitting governments to "coordinate emergency response and assistance in the event of a nuclear accident" releasing radioactivity into neighboring countries.

The statement also suggested the convening at an early date of a governmental conference to discuss a wide range of nuclear safety issues.

In contrast with current agreements, the proposed accords would contain a number of mandatory provisions. If adopted, they would mark an acknowledgement by the international community that the control of nuclear power is too important to be left entirely to individual nations.

This one-day emergency session of the IAEA Board of Governors was the first such international meeting since the April 26 fire and explosion at Chernobyl, which have been widely described as the world's most serious nuclear accident.

Addressing the board, the deputy chairman of the Soviet nuclear power ministry, Boris Semyonov, said that 15 persons have died as a result of the accident. This is the highest casualty figure yet provided by a senior Soviet official. Soviet leader Mikhail Gorbachev mentioned nine deaths in a televised address last week.

Officials here said that the cooperation at today's meeting of the IAEA, a United Nations agency, resulted in part from the conciliatory tone of Gorbachev's statement. In an apparent attempt to defuse western concern about the release of radioactivity, the Kremlin leader said that the Soviet Union would favor increased international cooperation on nuclear energy, including an early warning system in the event of accidents.

The seven leading industrial democracies meeting in Tokyo recently also called for improved international reporting on nuclear accidents that affect other countries.

Until now, the main task of the IAEA has been to prevent the proliferation of nuclear weapons by monitoring the cycle of uranium, plutonium, and other radioactive elements in civilian reactors. Responsibility for plant safety has been left to the 26 countries that operate the world's 374 nuclear power plants.

Comments by delegates at today's meeting suggested that there is still considerable resistance to binding international safety standards for nuclear power. Semyonov told journalists that he preferred the idea of "guidelines" to "standards," and French officials also insisted that regulation on nuclear safety -- as opposed to a mandatory early warning system and emergency assistance -- should be left to individual governments.

France, which uses nuclear power to generate 65 percent of its electricity, has traditionally been reluctant to accept outside controls. It is the world's second largest producer of nuclear energy after the United States.

A more flexible position was taken by West Germany, where the government is under political pressure to show that it is taking effective steps to promote nuclear safety. A letter was distributed to delegates from Chancellor Helmut Kohl offering to host an international conference on nuclear energy later this year.

Support for an international conference also came from the director general of the IAEA, Hans Blix of Sweden, who led a three-man delegation to Moscow last month. Blix proposed a separate IAEA conference on nuclear safety immediately after the agency's annual general meeting in September.

Noting that present safety standards were purely voluntary, Blix said that governments might wish to examine the possibility of adopting "binding minimum standards." He added, however, that responsibility for nuclear safety must remain with national governments.

Tonight's statement also called for a "post-accident review meeting" to be held within three months to analyze data from Chernobyl. Blix said that the Soviet Union had agreed to cooperate with a post-accident analysis under the auspices of the IAEA.