(AP Photo/J. Scott Applewhite)

WASHINGTON - The top U.S. military leader said Tuesday that he pleaded with Egypt's ruling generals to resolve the crisis with Washington over the crackdown on American non-profit groups that promote democracy in the Middle East, warning that the simmering dispute threatens billions in U.S. aid and the relationship between the two nations.

Army Gen. Martin Dempsey, in testimony before the Senate Armed Services Committee, stopped short of saying whether his appeals during a recent trip to Egypt swayed the generals to drop charges against pro-democracy workers.

Egypt recently referred at least 16 Americans, including the son of U.S. Transportation Secretary Ray LaHood, and some two dozen other employees of pro-democracy non-profit groups to trial before a criminal court. The Americans were accused of illegally using foreign funds to foment unrest in the country.

"I spent about a day-and-half in conversation with them, encouraging them in the strongest possible terms to resolve this so that our military-to-military relationship could continue," Dempsey told the committee. "I am convinced that potentially they were underestimating the impact of this on our relationship. When I left there, there was no doubt that they understood the seriousness of it."

Dempsey said his trip had been planned prior to the crackdown on the non-profit groups. He met with his counterpart Lt. Gen. Sami Anan and top Egyptian military leader, Field Marshal Hussein Tantawi.

"I explain to them that I was coming there to talk to them about our (military) relationship, about Syria, about Lebanon, about the Sinai, but that I couldn't do that because we had this issue that was an impediment to that," he said.

Egypt and the United States have been close allies for more than three decades. But Cairo's campaign against the pro-democracy groups could seriously damage relations with far-reaching ramifications in a region already shaken by the political realignments arising from Arab Spring revolts.

The substantial U.S. military aid to Egypt is linked to its adherence to an American-mediated 1979 peace treaty with Israel, Washington's closest Middle East ally. Egypt receives $1.3 billion in U.S. military aid and about $250 million in economic assistance every year.

Members of the House and Senate, furious with the latest developments, have raised the possibility of trying to withhold the aid. Sen. Rand Paul, a Republican, is pushing an amendment that would cut off U.S. assistance to Egypt unless it releases the Americans.