CAIRO -- U.S. diplomats scrambled Saturday to work out a deal that resolves criminal charges against 16 Americans in Egypt on the eve of their scheduled trial in a case that has threatened to upend the 30-year alliance between Washington and Cairo.
U.S. officials said Saturday night that they still could not predict what would happen when the trial opens Sunday.
U.S. diplomats, Egyptian lawyers, and others involved in the case said efforts foundered amid a breakdown in the lines of authority in the military-led transitional government, which is in its final months before the generals have pledged to leave power.
U.S. officials say they have tried to find Egyptian counterparts who might intercede, but Egyptian leaders say they cannot intervene in the judicial process.
If the case is not resolved, Congress and the Obama Administration have vowed to cut off the $1.55 billion in annual aid to Egypt, potentially rupturing the alliance among United States, Egypt, and Israel that has been a linchpin of regional stability.
A senior U.S. official said the Obama Administration is in "intense discussions" with Egypt to resolve the legal case "in the coming days."
The U.S. official said Secretary of State Hillary Clinton had raised the matter twice in person with Egypt's foreign minister -- once in London and once in Tunisia -- in the past three days.
The 16 Americans and 27 others face criminal charges of working for unlicensed nonprofit groups and accepting foreign money to operate them.
Nine of the Americans were outside Egypt when the charges were filed.
Egypt barred the remaining seven, including Sam LaHood, the son of the U.S. Secretary of Transportation Ray LaHood, from leaving Egypt.
The seven Americans work for a pair of federally financed nonprofit groups with close ties to the congressional leadership, the International Republican Institute, and the National Democratic Institute, which are chartered to promote democracy abroad.
Egyptian prosecutors accuse the groups of collaborating with the CIA to destabilize Egypt and manipulate its revolution for the benefit of the United States and Israel.
If convicted, the accused face a fine and up to six years in prison for working for unlicensed nonprofit groups and a minimum of six years for receiving money from abroad.
It is not clear whether the Americans and the rest of the defendants will appear in court Sunday. They could not be reached by phone.
As of Saturday, the seven Americans in Egypt had taken refuge in the U.S. Embassy for fear of arrest, officials said.
U.S. officials dismiss Egypt's allegations of subversive aims as grandstanding playing to anti-U.S. sentiment.
The officials say it is implausible that the United States would give about $15 million a year to have the two groups undermine the Egyptian state when it spends more than $1 billion a year to support the Egyptian military.
There is no dispute that the two groups and their staffs have broken the letter of Egyptian law. Both groups sought, but never received, licenses from the Egyptian government, and both are openly financed from abroad.
They therefore violate two restrictions on civil groups left over from the government of Hosni Mubarak, the president who was deposed a year ago.
But both groups had been tolerated in Egypt for years, along with scores of Egyptian nonprofit groups that also break both rules.
Last week Sen. John Mc- Cain, chairman of the International Republican Institute, left a meeting in Cairo with Egypt's top military rulers assured that a resolution was close at hand, people briefed on the meeting said.
U.S. officials say they are seeking some kind of resolution that might free the seven Americans trapped in Egypt while saving face for the Egyptian authorities.
Egyptian lawyers have suggested that the security agencies responsible for overseeing nonprofit groups could grant licenses to the U.S. groups, signaling to the presiding judge that their activities were not threatening and light sentences would be in order.