If the talks should disintegrate into rancorous arguments, as lower-level talks did last August in Banjul, Gambia, then the bloody civil war is likely to continue.

The idea of a merger was born, Mr. Raymond said in the interview yesterday, during lower-level talks earlier this year about combining refining operations in Japan.

The two bodies have held four rounds of lower-level talks since last year, but all collapsed after they touched on the issues of sovereignty and jurisdiction.

Despite that, under his rule, Iran has held lower-level talks with US officials, particularly in multilateral gatherings for efforts to stabilise Afghanistan.

They also agreed to open lower-level talks on June 21 in Seoul, where the nuclear issue is certain to be discussed again.

But Mr. Eizenstat's unusual, direct appeal to Mr. Cotti, and lower-level talks between American and Swiss diplomats, had echoes of an earlier time.

He said lower-level talks would be held next week involving technical experts from the two countries, and added: "We made very little progress today.

But he had argued that more groundwork needed to be laid in lower-level talks before a useful summit meeting could be held.

Those lower-level talks have now reached their limit.

Officials said they would do nothing more on those topics than they did in lower-level talks.