Egypt's decision to bring criminal charges against 19 Americans and other activists is deepening a rift between Washington and Cairo at a time of growing instability in the Middle East. The charges are tied to an investigation into illegal foreign funding of non-governmental organizations.

The heady, early days of Egypt's Arab Spring blossomed in Tahrir Square in Cairo.

It's where thousands of Egyptians gathered daily - the square's wide expanse serving as a grand stage for the nation's democratic aspirations.

But as a new spring approaches, a new drama unfolds, just blocks away at the U.S. Embassy.

There several Americans are holed up, charged with undermining Egypt's democratic transition.

Prime Minister Kamal al-Ganzouri defends the case against them, despite the risk of losing U.S. aid because of it. "Egypt will abide by the law and implement it. Egypt has known civilization for thousands of years, so it can never go back because there is or there is not aid," Mr. al-Ganzouri said.

U.S. Deputy Assistant Secretary of State Aaron Snipe says the Obama administration is deeply disappointed.

"The government of Egypt's decision to charge these Americans will have consequences. We think that we must remain engaged because we value this relationship with the Egyptian people and the Egyptian government. We've got differences, for sure, and there are some real challenges that we have got to overcome," Snipe said.

Most of the Americans were in Cairo supporting an electoral process to choose new lawmakers following the uprising against Mr. Mubarak. U.S. officials say they were supporting elections, not specific candidates or parties.

But Egyptian Judge Sameh Abu Zaid says that's not true. "The activities were mainly political and concerned the training of political parties and rallying voters' support for one candidate or the other," Zaid said.

Prime Minister al-Ganzouri says the foreign groups interfered in Egyptian affairs. "What is happening has, to a great extent, a methodology, and there are those who are directing it, and I don't know why it is thus being directed. Is it for the purpose of toppling military rule? If so, what happens after that?," he said.

Brookings Institution visiting fellow Khaled elGindy says holdovers from the ousted Mubarark government are using the charges to distract from popular discontent in Cairo. "They have tried to pin the blame on outside influences, foreign agendas, and, basically, ginning up (creating) these conspiracy theories. And so, over time, eventually they have had to put names and places on these conspiracy theories, and the convenient scapegoats are these NGOs, who, frankly, have been working in Egypt even before last year's uprising," elGindy said.

U.S. officials say the case has broad implications for relations between Washington and Cairo - not only military assistance, but support for Israeli-Palestinian peace talks as well as efforts to end the violence in Syria.