CAIRO — Egypt will begin criminal proceedings on Friday against 19 Americans and two dozen others in a politically charged investigation into the foreign financing of nonprofit groups that has plunged relations between the United States and Egypt to their lowest point in three decades, state news media reported Saturday.

The trial escalates a confrontation that has shaken the 30-year alliance between Cairo and Washington, a cornerstone of the American-backed regional order since the Camp David accords were signed in 1978. American officials have said the prosecution jeopardizes the disbursement of more than $1.5 billion in foreign aid to Egypt, the bulk of which is assistance to the military, which has governed the country since the ouster of the longtime leader Hosni Mubarak a year ago.

The 43 defendants have been charged with operating local offices of international organizations without the requisite licenses and illegally receiving foreign funds, state news media reported.

The American defendants work for four United States-based groups, two of which, the National Democratic Institute and the International Republican Institute, are chartered as democracy-building organizations and have close ties to leaders in the United States Congress. The other two organizations are Freedom House and the International Center for Journalists.