"We have all been focused over these past few weeks on the NGO issue, and it is a matter of serious continuing concern for the United States," State Department spokeswoman Victoria Nuland said in a statement.

"But it is also important to underscore that the United States remains committed to a strong bilateral relationship with Egypt."

"Despite the recent strains, and differences on certain issues, the fundamentals of this strategic relationship remain strong," she added.

Some 43 foreign democracy activists working for non-government organizations are accused of receiving illicit foreign funds to operate without a license and Egyptian media reported Saturday that their trial would restart on 8 March.

At least13 foreign NGO workers, including several Americans, were allowed to leave Egypt on Thursday after the authorities lifted their travel ban. The other defendants are Egyptian, Palestinian, Norwegian, Serbian and German nationals.

Egypt and the United States "continue to work together to protect regional peace and security and to address the full range of regional issues before us," Nuland said.

"The United States and Egypt have been close partners for many decades, and we look forward to a close partnership for many decades to come."