Washington "deeply regrets the use of air power by Ethiopia in the current conflict, in particular against economic targets and near civilian population centers," State Department spokesman James Foley said in a statement.

"We urge (Ethiopia) to resume the (air power) moratorium immediately (and) also urge the Eritrean authorities to continue to uphold their commitment to the terms of the moratorium."

The State Department call came as Asmara criticized the international community for its silence over Ethiopian air strikes and renewed warnings that it reserved the right to respond in kind.

Eritrea claimed that four civilians had been killed Sunday when Ethiopian warplanes bombed a village.

Ethiopian planes also bombed the airport at Eritrea's Red Sea port of Assab, in the east, at dawn on Sunday, both sides confirmed.

Sunday's were the first attacks reported since Tuesday last week in the sporadic fighting over the ill-defined border which resumed on February 6 after a lull of seven months.

No reports came in of any fighting along the 1,000-kilometer (600-mile) border on Monday.

The initial fighting began in May last year but petered out after about five weeks as diplomatic efforts to resolve the crisis took over.

The United States, European Union and United Nations all back a peace plan presented by the Organization for African Unity in November which calls for the deployment of peacekeepers and neutral delineation of the border.

The plan has stalled over a clause demanding that Eritrea first withdraw its troops from positions they occupied in May.

A delegation representing the EU visited Asmara and Addis Ababa on Friday and Saturday, but was unable to win agreement for a ceasefire as a prelude to further negotiations.