At least 300 supporters of Abu Bakr Bashir were on their way to Jakarta from his home region around Solo in Central Java, said Fawzan al-Ansuri, spokesman for the Indonesian Mujahidin Council.
But Jakarta police said there were no plans to strengthen security for the verdict. "The security arrangements remain the same as the usual," a spokesman said.
Bashir is relaxed and ready to hear the court's decision, his lawyer said on Monday, even though he could face a life sentence if convicted of trying to topple the government and set up an Islamic state.
Prosecutors say the Muslim cleric heads the Jimaah Islamiyah (JI) which they claim is linked to al-Qaida.
JI is also accused of church bombings which killed 19 people on Christmas Eve 2000, the Bali blasts last 12 October which killed 202 people and the 5 August Jakarta hotel blast that claimed 12 lives and a string of other attacks.
But Bashir is not accused over the Bali bombing. He is charged with approving the Christmas Eve attacks, a foiled bombing campaign in Singapore, and an aborted plot to kill Megawati Sukarnoputri before she became president.
He says he was framed by the United States and other enemies of Islam because he was struggling to introduce Islamic sharia law in Muslim-majority but secular Indonesia.
One of Bashir's lawyers, Mahendradatta, told journalists his client was convinced his trial and the accusations against him "were set up by [US President] George Bush" and maintained his innocence.
Letter to America
Bashir: If I fight you with force
[Bush], I will just be like you
In July, the suspected JI leader tried to send Bush a letter through the US embassy, telling him that "I have never known or even more, approved, any bombings."
"That is not my way to fight you [Bush] ... If I fight you with force, I will just be like you," his lawyer said, quoting from the letter. It was not immediately clear if the letter was passed on.
Mahendradatta added his client "has no intention to compromise" and firmly believes that "justice is not in the hands of men but of Allah."
Bashir's supporters have stuck by him through his trial. The Mujahidin Council, which seeks sharia law, last month unanimously reappointed Bashir as its leader for another four years.
On Sunday evening more than 1,000 supporters rallied in Solo to pray that the cleric be given strength to face the verdict, al-Ansuri said.
"The participants also prayed for the judges to be able to come up with a fair verdict," he told journalists.