The judges in the trial in Egypt of 43 people, including 19 Americans and other foreigners, over the funding of non-governmental groups, have resigned.
The case caused a serious rift with the United States after police in Cairo raided several NGOs in December.
Some of them are backed by US groups. Egypt says they received illegal foreign funding and stopped the accused from leaving the country.
Egyptian media said the three judges resigned in "embarrassment".
The precise reasons for the move remain unclear.
US officials had earlier said the case was putting at risk the $1.3bn military aid it sends to Cairo each year.
On Tuesday, US Secretary of State Hillary Clinton suggested the two sides were moving towards a resolution.
She said "very intense discussions" on the issue were taking place.
"We've had a lot of very tough conversations and I think we are moving toward a resolution," she said.
Egyptian prosecutors confiscated documents and computers when they raided the NGOs in late December. Their members were charged with obtaining international funds illegally and failing to register with the government.
The son of US Transport Secretary Ray LaHood is among those facing criminal charges.
Sam LaHood heads the Egyptian office of the International Republican Institute (IRI).
The IRI and the National Democratic Institute (NDI), loosely associated with the US Republican and Democratic parties, were among 17 US-based and local foreign-funded groups whose offices were raided.
The trial has been adjourned to the end of April.