The rainy season has ended in the Horn of Africa, where Ethiopia and Eritrea are fighting for a dusty corner of remote terrain. Hardening ground has brought an increase in supply, ammunition and tank traffic. And in the trenches that line the disputed border, hundreds of thousands of troops wait for the human waves to start again.

"Everybody knows what is happening," said Yemane Ghebremeskel, a spokesman for the government of Eritrea. "There is a buildup of forces."

The rising tension in the obscure 18-month-old conflict has generated a fresh flurry of diplomatic activity aimed at preventing a resumption of all-out warfare. Last week, U.S. officials joined diplomats from the Organization of African Unity in visits to Addis Ababa and Asmara, the capitals of the rival nations.

Both Ethiopia, with a population of 60 million, and Eritrea, with one-twentieth that number, have accepted an OAU peace plan, but for reasons as unclear as the cause of the conflict the accord has not been implemented by either side.

Eritrea appeared to make a fresh overture Monday. Saying that his country would not be hung up on details, President Issaias Afwerki seemed to indicate in an interview with the Reuters news agency that Eritrea is prepared to pull back its troops unilaterally.

A U.S. official called the remarks encouraging. "I think these guys have made a strategic decision to resolve this somehow peacefully," said the official, who asked not to be identified. The Issaias interview, the official said, was an effort "to see how the Ethiopians respond to flexibility--verbal flexibility."

The Ethiopian response came today. In a terse statement headlined, "Eritrea: All Talk, No Action," the government challenged Asmara to "move beyond talk and take practical actions that unequivocally demonstrate its commitment to withdraw." Eritrea replied that it would not, and the situation remains where it has been for 18 months--deadlocked in trenches along a 600-mile border.

At stake in the stalemate--besides pride--is a patch of about 160 square miles claimed by both countries, which two years ago were close allies. The first skirmishes flared after Eritrea sent tanks into the disputed area in May 1998, and hundreds of troops died on both sides after Ethiopia marshaled its forces a month later. But the bloodiest battles came in February. In an offensive that military analysts described as World War I tactics backed by modern weapons, Ethiopia sent waves of infantry into the no man's land between the trench lines.

After four days of fighting, the Eritrean positions were overrun and Ethiopia reclaimed Badme Plain, the largest portion of the area under dispute. The death toll ran into the thousands, possibly tens of thousands, according to independent Western analysts.

Since then, death counts have become part of the dispute. Eritrea said Sunday that 70,000 Ethiopians have lost their lives on the battlefield. Today, Ethiopia called that figure "patently false" and claimed that Eritrean killed and wounded have topped 100,000.

"We've been waiting for the conflict to be settled peacefully," said Haile Kiros, a spokesman for the Ethiopian government. He pointed out that Ethiopia was first to accept the OAU peace plan and has objected only to a technical agreement that he said "diluted" the original.

"If the Eritreans do not accept it, we have no other alternative than to use all means available to recover our territory from the aggressor," Kiros said.