Senator John McCain (R-AZ) said he will travel to Egypt with a group of senators to try and diffuse a worsening standoff over Americans being tried for their work with pro-democracy organizations.

Nineteen U.S. citizens have been formally charged in connection with their work for non-governmental organizations that Egypt says are operating illegally. Relations between Egypt and the United States have steadily deteriorated since Egypt began investigating the groups, and American officials have threatened to withhold the $1.55 billion in military aid to Egypt allocated for 2012.

Congressional support for Egypt -- including continued financial assistance -- is in jeopardy, McCain said in a joint statement with Senator Kelly Ayotte (R-NH) and Senator Joseph Lieberman (I-CT). A rupture in relations would be disastrous, and the risks of such an outcome have rarely been greater.

Egypt's military leaders have been defiant in the face of such threats, saying they will not be deterred by the possibility of suspended aid.

Egypt will apply the law, Prime Minister Kamal al-Ganzouri said at a Tuesday news conference, adding that the government will not back down because of aid or other reasons.

The confrontation has renewed criticisms of the military government that assumed power in Egypt after the fall of longtime leader Hosni Mubarak. Many in Egypt believe the current regime has perpetuated many of Mubarak's abuses by violently repressing protests and appearing resistant to relinquish power to a civilian government. Fayza Abul Naga, a minister of planning and international cooperation who has spearheaded the prosecutions, is a holdover from the Mubarak era.