This court sketch shows Nadarasa Yogarasa, who is among the Tamil-Canadians charged with trying to buy rockets and weapons for the Tamil Tigers separatist group in Sri Lanka. (Christine Cornell/CBC)

U.S. prosecutors are seeking tougher sentences for three Tamil-Canadians who were caught by the FBI trying to buy anti-aircraft missiles and other weapons for the Tamil Tigers three years ago.

Toronto residents Suhil Sabaratnam and Thiruthanikan (Thani) Thanigasalam were due in court for a sentencing hearing in New York on Monday. Both have pleaded guilty to conspiracy and material support for terrorism and were facing possible sentences of 25 years to life. Two others — Nadarasa Yogarasa, also a Canadian resident, and Sathajhan Sarachandran — have pleaded guilty in connection with the undercover FBI sting operation.

The proceedings were postponed until Jan. 22. because the prosecutors want heavier sentences. They're arguing that in addition to the current charges, the men's plan to buy the weapons constituted an act of domestic terrorism.

Domestic terrorism, as defined in the Patriot Act, "involve acts dangerous to human life that are a violation of the criminal laws of the United States or of any State."

The defence lawyers insist the illegal arms would not have been used against Americans or in the U.S. and the men's actions should not be considered domestic terrorism.

On Aug. 19, 2006, the men drove from Toronto to Long Island, N.Y., to meet "Vinny," a man they believed was a Mafia arms dealer but was actually an undercover FBI agent.

The agent showed Sabaratnam and Thanigasalam a crate containing a Stinger missile and its firing tube.

After making a cellphone call to Tamil Tiger bosses in Sri Lanka, Thanagasalam ordered 10 SA-18 heat-seeking anti-aircraft missiles and launchers, 500 AK-47 assault rifles and other military equipment, the FBI said.

The weapons were to be used by the Liberation Tigers of Tamil Ealam, or LTTE, to shoot down Kfir aircraft used by the Sri Lankan military, the FBI said.