CAIRO, EGYPT (CNN) - A delegation of three U.S. senators, including Arizona Sen. John McCain, were in Egypt on Monday to meet with the country's military leaders and discuss the case of 19 American workers who face charges as part of an Egyptian crackdown on nongovernmental organizations.

"I think this is a very difficult situation," McCain told ABC's This Week. "I am not a negotiator, but I think it's important that I and the other senators in the delegation explain to the Egyptian leadership ... that this is a serious situation, has serious implications for our relationship."

The delegation also includes Sens. Lindsey Graham of South Carolina and Joe Lieberman of Connecticut. The visit is part of a pre-planned trip.

McCain said that while he will address the situation of the detained Americans, he will not attempt to negotiate their release.

"That is the job of the administration, but we will have conversations with military leaders and others who I have known for many, many years on a personal basis," he said Tuesday on Capitol Hill.

The Americans are among 43 people accused in a case involving foreign funding. They are scheduled to appear in a criminal court Sunday, the spokesman for the Egyptian general prosecutor's office said.

Among the Americans is Sam LaHood, the son of U.S. Transportation Secretary Ray LaHood, who serves as director of Egypt operations for the International Republican Institute.

McCain serves as board chairman for the IRI, which describes itself on its website as a nonprofit and nonpartisan organization that "advances freedom and democracy worldwide by developing political parties, civic institutions, open elections, democratic governance and the rule of law."

In December, authorities carried out 17 raids on the offices of 10 organizations, including the U.S.-based Freedom House, National Democratic Institute (NDI) and the IRI.

Freedom House's website says it "supports democratic change, monitors freedom and advocates for democracy and human rights around the world," supporting nonviolent civic initiatives in societies where freedom is threatened. The NDI says it works to support and strengthen democratic institutions worldwide "through citizen participation, openness and accountability in government."

Adel Saeed, a spokesman with the general prosecutor's office, said the raids were part of an investigation into allegations that the groups had received illegal foreign financing and were operating without a proper license.

The groups have denied any wrongdoing. The IRI has said the prosecution is a "politically motivated assault" that "reflects escalating attacks against international and Egyptian democracy organizations." While Egypt may call the situation "a legitimate judicial process ... the continued assault on American, German and Egyptian civil society is not a 'legitimate judicial process,'" the IRI said.

"We're being accused of things we've never done," IRI President Lorne Craner said last month. "We are told we have operated without registration, and that is true because we filed our registration papers five and a half years ago. We were told the papers are complete and we're still waiting."

Similarly, NDI said it applied for registration in 2005 through the Egyptian Ministry of Foreign Affairs, "and has fulfilled all of the registration requirements for the past six years, including a number of updates provided in January." The group said it will "vigorously defend the accused personnel."

"Despite promises made by Egyptian authorities to the highest levels of the U.S. government, we remain closed, our computers, files and cash still in the possession of the Ministry of Justice, and our staffs face hostile interrogations by investigating judges, and now the prospect of arrest and imprisonment," Freedom House President David Kramer testified last week before the House Committee on Foreign Affairs. "Nowhere else in the world has any of our offices been treated as they are in Egypt."

The U.S. State Department said last week it had received a 24-page document from Egyptian authorities that lays out the charges against the staff of U.S. and international democracy-building groups.

The employees of the American and European NGOs have been charged with operating in Egypt without licenses. An investigation by authorities revealed that the organizations received millions of pounds from abroad under the names of NGO employees and not through their official bank accounts.

Ashraf El-Ashmawi and Sameh Abu Zeid, the two judges handling the cases, said the charges could lead to five-year prison sentences.

"These organizations conducted unlicensed and illegal activities without the knowledge of the Egyptian government," El-Ashmawi said. "Documents confiscated during the raids on the NGOs offices confirm illegal foreign funding."

Documents also showed that foreign workers employed by the NGOs deliberately had tourist - not work - visas, and did not pay taxes, prosecutors said.

Egyptian officials have blamed continuing unrest in their country on foreign interference they attribute, in part, to the organizations.

The crisis has jeopardized U.S. aid to Egypt and strained relations between the two nations. In a Feb. 2 letter to Secretary of State Hillary Clinton and Defense Secretary Leon Panetta, 41 members of Congress urged the administration to withhold further aid to Egypt until the country's leadership lets the organizations reopen and returns seized property.

The situation may have been fueled by a sense of nationalism on the part of Egypt's military-led government, which assumed control following the ouster of longtime President Hosni Mubarak a year ago, said Isobel Coleman, a senior fellow at the Council for Foreign Relations.

"It's better in the short term to be seen as standing up to the Americans," she said earlier this month. "... As the situation continues to be very unsettled in Egypt, the powers that be will look for a scapegoat. Blame your problems on outside powers. That's how it has been throughout history."

But both sides have "painted themselves into a corner," said Marina Ottaway, a senior associate at the Middle East program of the Carnegie Endowment for International Peace. The Egyptians have made a legal case, she said, and the Americans will find it difficult to tell them to interfere with the work of the judiciary when they are trying to push democracy.

Briefing reporters Friday, State Department spokeswoman Victoria Nuland said that its legal team has held a number of meetings on the situation.

"We continue to work very hard on these issues. So we need to let that work go forward and hope we can solve this," she said.

Nuland has said no speedy resolution of the case was expected.

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