A 24-year-old Muslim man in New Jersey admitted that he conspired to provide support to the Islamic State (ISIS) jihadist group by forming an army to join the group and then launching an attack on the White House.

Alaa Saadeh of Rutherford pleaded guilty before US District Judge Susan Wigenton of New Jersey to the charge. He remains detained without bail.

He said before he was arrested on June 29, he planned to travel overseas to join ISIS along with others. He discussed the plan with his brother Nader Saadeh, Samuel Rahamin Topaz and Munther Omar Saleh, and told the judge that each of them indicated that they wanted to join ISIS at various times.

Saadeh also admitted that he watched ISIS-related videos with Nader and Topaz, some of which depicted the execution of individuals – both Muslim and non-Muslim – regarded by ISIS as enemies.

After taking custody of Nader in August, the FBI said he sent "electronic messages expressing his hatred for the United States and desire to form a small army that would include their friends."

"Saadeh conspired with his brother and others to travel overseas to join ISIL (US term for ISIS)," said Assistant Attorney General John Carlin said, according to the Christian News Network.

"Saadeh further admitted assisting Nader Saadeh with these plans by letting him purchase airline tickets using Saadeh's credit card, removing the SIM card from Nader's smartphone and resetting the smartphone in an effort to avoid detection," the FBI said.

"After becoming aware that the FBI was investigating this matter, Saadeh instructed an individual who knew of Nader Saadeh's support for ISIL to lie if questioned by the FBI on the subject," it said. "Saadeh further admitted telling this individual to 'just play stupid,' 'pretend it never happened' and 'keep it honest up to a point.'"

Saadeh will be sentenced in February 2016 and faces up to 15 years in prison. Last September, Topaz also admitted the charge.

Topaz, NJ.com reported, told his lawyers that the group planned to stage a small attack on the White House "since they could not leave the US."

Khaled Saadeh, Alaa and Nader's father, who lives in Oman, said that he urged his boys to come to Jordan in order to keep them from joining ISIS. He is opposed to his sons' actions.

"I did what I have to do like a father to protect my sons, but the government is not doing enough to protect our kids from this kind of group, who try to brainwash our kids," he said.

Saadeh's mother also begged them not to "go anywhere if you love me."