The men - all Muslims from the Washington, D.C., area - pleaded not guilty to a total of five charges, the most severe of which carries a maximum sentence of life in prison, defense lawyer Hasan Dastagir told The Associated Press.
"My clients were in good shape and high spirits," Dastagir said.
The men, aged 19 to 25, were charged by an anti-terrorism court inside a prison in Sargodha, the city in Punjab province where they were arrested in December. They were reported missing by their families in November after one left behind a farewell video showing scenes of war and casualties and saying Muslims must be defended.
Their lawyer has said they were heading to Afghanistan and had no plans to stage attacks inside Pakistan.
The court also charged the men with planning attacks on Afghan and U.S. territory, said Dastagir. The charges did not specify what was meant by U.S. territory but could be a reference to American bases or diplomatic outposts in Afghanistan.
The men also were charged with contributing cash to banned organizations to be used for terrorism and with directing each other to commit terrorist acts.
"This last charge carries life in prison while the rest of the charges have lesser punishments," Dastagir said.
The trial will begin on March 31, and the prosecution is slated to present more than 20 witnesses, Dastagir said.
The defense plans to bring witnesses from the U.S. and provide evidence of community service carried out by the men back home, Dastagir said.
Pakistani police have publicly made several accusations against the young men, claiming the suspects contacted Pakistani-based jihadi groups. They accused the five of using the social networking site Facebook and video-sharing site YouTube while they were in the U.S. to try to connect with extremist groups in Pakistan.
During past court hearings, the men have claimed they were tortured by Pakistani police and FBI agents. Pakistan and the U.S. have denied those allegations.
The U.S. has pressed an often-reluctant Pakistan to crack down on militants in its territory, many of whom are believed involved in attacks on American and NATO forces across the border in Afghanistan. At the same time, several recent cases have highlighted incidences of foreigners signing up to join the insurgents on both sides of the border.
Two of the detained Americans are of Pakistani origin, while one is of Egyptian, one of Yemeni and one of Eritrean descent.
