The trial of 43 pro-democracy activists, including at least 16 Americans, is due to begin in Egypt.
They are accused of receiving illegal funding from foreign governments, including the US.
The case has severely strained relations between Egypt and the United States, with threats that US aid could be cut.
The two countries are holding talks to try to solve the case, a senior US official said on Saturday.
“We are in intense discussions with the government of Egypt to try to resolve the situation with the NGOs within days,” the official was quoted as saying by the Associated Press news agency.
A number of the Americans have taken refuge in the US embassy after being refused permission to leave Egypt. Some defendants were already abroad when the travel ban was ordered.
It is not clear if any of the accused Americans will appear in court.
Reports are mixed as to whether 16 or 19 US citizens are charged in the case.
The other defendants are also said to include Egyptians, Germans, Palestinians, Norwegians and Serbs.
The International Republican Institute (IRI) and the National Democratic Institute (NDI) – both loosely associated with the US Republican and Democratic parties – as well as Freedom House and the German Konrad-Adenauer Foundation were among 17 local and foreign NGOs whose offices were raided by prosecutors in late December, seizing documents and computers.
Among the accused are Sam LaHood, head of Egypt operations for IRI and son of US Secretary of Transportation Ray Lahood.
The charges mainly revolve around operating illegally in Egypt and receiving foreign funding illegally, David Kramer, president of Freedom House, said.
“In order to apply for registration to operate legally, organisations need to set up an office, to hire a staff and to have activities, and we believe on that basis we were operating in full accord with Egyptian law,” he told the BBC.
Human rights groups have strongly criticised the Egyptian investigation. They say the charges are part of an orchestrated campaign to silence groups critical of Egypt’s ruling Supreme Council of the Armed Forces (Scaf).
The case has provoked loud protests from Washington, and even threats to cut off the $1.5bn (£1bn) of aid paid to Egypt each year.
But inside Egypt, the raids and arrests have won widespread popular support, relieving some of the pressure on the military council as it moves towards a handover of power to civilians in the coming months, the BBC’s Jon Leyne in Cairo reports.
One Egyptian minister has accused the organisations of trying to spread chaos in the country.
Correspondents say that since the fall of President Mubarak, hundreds of Egyptian NGOs have also come under investigation from the government.