Egypt - 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.