The decision by the Defence Council, comprising the Chief of the Defence Staff, Major-General Abdulsalam Abubakar, and the heads of the air force, army, and navy, could determine whether the international community imposes economic sanctions against Nigeria and whether the Commonwealth will move to expel Africa's most populous nation. The council's judgment will be passed on to the governing Provisional Ruling Council (PRC), which has the final word.
The United States suggested last week that if the Abacha government carried out the sentences against the alleged plotters, it would consider tightening a mild package of sanctions that was imposed by Western countries after the army cancelled presidential elections in June 1993.
The US buys 50 per cent of Nigeria's daily oil production of 1.9 million barrels. The powerful African American lobby group, Transafrica, has urged the Clinton administration to impose an embargo on Nigerian oil exports, which account for 90 per cent of the country's foreign-exchange earnings.
The impact could be devastating to Nigeria, which already has a $37bn (pounds 23bn) foreign debt, widespread unemployment, and a manufacturing capacity that is running at less than 30 per cent.
"It will only aggravate the Nigerian situation, for instance, the people we are trying protect and defend will be the final point of impact," a presidential spokesman, David Attah, said in an interview published by a local newspaper, This Day, on Sunday.
Western governments have also suggested that they may be prepared to freeze the assets held abroad by present and former military officers and civilians who have siphoned off Nigeria's oil revenues. A recent report by a government-appointed commission found that $12bn in oil income could not be accounted for.
The international criticism has irked the Abacha government. The Foreign Minister, Tom Ikimi, issued protests last week to Washington and to Britain, in which Nigeria demanded "that our sovereignty is respected by other nations".
There were signs at the weekend, however, that the intense diplomatic pressure was beginning to tell on the military authorities. The government's number two, Lieutenant-General Oladipo Diya, told the visiting South African Deputy President, Thabo Mbeki, on Saturday that the PRC "will not hesitate to embrace every possible way of showing mercy where it is deserved".
The visit by Mr Mbeki, who brought an appeal for mercy from President Nelson Mandela, followed a visit by President Jerry Rawlings of Ghana, who was on a similar mission of mercy.
But appeals for clemency in the case of coup-plotting have had little success in the past. Since 1976, at least 115 people have been executed for attempting to overthrow the government. Ironically, a bloodless military coup brought General Abacha to power in November 1993. He had played a central role in previous army coups in 1983 and 1985.
General Abacha has promised to announce a timetable for a return to civilian rule on 1 October. But most human rights groups are sceptical. Their spokesmen have argued that there is no need for a transition programme, since Moshood Abiola, a flamboyant Muslim businessman who has been detained for the past year, won the presidency in the 1993 elections, which were declared free and fair by international observers.