In proceedings that lasted a brief five minutes, the court was told that Fai's main attorney Nina Ginsberg could not appear because of scheduling conflict.
Fai was represented by Ginsberg's deputy Michael Lieberman, while the government was represented by attorney Gordon Kromberg.
As he entered the courtroom, Fai waved to his family and friends present in the court. His wife, who is of Chinese origin, was also present.
The court in Alexandria then put off the detention hearing till next Tuesday.
The government attorney said the case is a bit complicated.
Fai's wife refused to give media interviews but told reporters informally that she has not been allowed to meet her husband since his arrest on Tuesday morning.
The FBI in its affidavit before the US court alleged that Kashmir-born US national received hundreds and thousands of dollars from the ISI and the Government of Pakistan with the sole objective of molding the view of American policy makers on Kashmir.
Fai, 62 and Zaheer Ahmad, 63, a US citizen and resident of Pakistan, face five years in prison if found guilty to the charges they are facing.