Egyptian judges probing alleged illegal foreign funding of non-governmental organisations accused domestic and foreign groups on Wednesday of illegally meddling in politics, further straining ties with key ally Washington.
The NGOs are operating "without licence," and their work "constitutes pure political activity and has nothing to do with civil society work," Judge Sameh Abu Zeid told a news conference.
The judge said December raids on 17 NGO offices as part of a probe into illegal funding had been conducted "according to the law."
"It is a very large and complicated case involving hundreds of people and organisations, Egyptian and foreign," he said.
He said dozens of people had been referred to trial because there was deemed to be enough evidence.
Among them are 19 Americans, a fact that prompted a trio of leading US senators to warn Egypt on Tuesday that the risk of a "disastrous" rupture in ties had "rarely been greater."
The United States, meanwhile, said it has been notified by Egyptian authorities of the formal charges against the US citizens in a document in Arabic of more than 100 pages.
"We now have a formal charging document," State Department spokeswoman Victoria Nuland told reporters in Washington. "We're working our way through it to understand who is implicated and ... what the expectations are."
And another official in Washington said the US military's top general plans to fly to Egypt this week, as the United States tries to press Cairo to lift the charges against the American nationals.
General Martin Dempsey, chairman of the Joint Chiefs of Staff, "is scheduled to travel to Egypt later this week," his spokesman Colonel Dave Lapan told AFP.
The "long-planned" visit includes meetings with his counterpart Lieutenant General Sami Enan and Egypt's military ruler, Field Marshal Hussein Tantawi, he said.
Abu Zeid said he had rejected a request from US Ambassador Anne Patterson to lift a travel ban on American NGO staff.
The groups being investigated include the US International Republican Institute (IRI), the National Democratic Institute (NDI), Freedom House and the German Konrad-Adenauer Foundation.
Following December's raids, several US members of the NGOs were barred from leaving the country, including Sam LaHood, the son of US Transportation Secretary Ray LaHood and the IRI's country director for Egypt.
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American officials said "a handful" of the pro-democracy activists subsequently took refuge inside the US embassy in Cairo, fearing arrest.
Abu Zeid said "there is much evidence, including witness accounts, expert accounts and confessions. There are 67 items of evidence."
"The foreign organisations are not civil society groups but branches of organisations based abroad," said Abu Zeid.
He said security agencies had repeatedly refused to register the NGOs, which "have been working in Egypt for years on tourist visas.
"They received orders from abroad to do this and were told not to get work permits. They also violated Egyptian tax laws."
He said the case involved illegal funding from the United States, Europe and also from Arab countries.
Investigations showed that their work "took another dimension after the January 25 revolution" that ousted president Hosni Mubarak last year, Abu Zeid said.
"Money was transferred to the organisations through a range of ways, including in individual accounts of employees, instead of in bank accounts in the organisation's name; or through money transfer companies," he said.
Those charged face up to five years in jail, according to Ashraf Ashmawi, another judge involved in the case.
Egypt's military junta, which took power after Mubarak was toppled, has accused foreign groups of funding street protests against them.
On Tuesday, US Republican senators John McCain and Kelly Ayotte, joined by independent Joe Lieberman, warned that US congressional "support for Egypt -- including continued financial assistance -- is in jeopardy" over the case.
Washington provides some $1.3 billion (981 million euros) a year in aid to Cairo -- one of the biggest aid packages offered to any nation.
"The current crisis with the Egyptian government has escalated to such a level that it now threatens our long-standing partnership," they wrote in a joint statement.
"There are committed opponents of the United States and the US-Egypt relationship within the government in Cairo who are exacerbating tensions and inflaming public opinion in order to advance a narrow political agenda," they said.