CHICAGO: A Pakistani-American pleaded not guilty to helping plan the deadly 2008 Mumbai attacks and plotting to attack a Danish newspaper which published cartoons of the Prophet Mohammed.

David Coleman Headley, 49, is accused of being a scout for two different Pakistan-based terrorist groups who used a friend's Chicago-based immigration company as a cover for his surveillance activities inIndia and Denmark.

A large man with greying hair and a relaxed manner, Headley stood tall in an orange prison jumpsuit after shuffling into a Chicago courtroom, his ankle shackles clinking.

He said little in his first appearance since his October 3 arrest, leaving it to his attorney to enter the not guilty plea and waive his right to be indicted by a grand jury.

Prosecutors have said that Headley is cooperating with the investigation into both plots, but his lawyer declined to say whether he was working on a plea deal.

Headley could face the death penalty if convicted of all 12 charges laid against him.

"These are very serious charges, and we are treating them very seriously," defense attorney John Theis told reporters after the brief arraignment.

"We'd like to respect our client's wish that we not comment on the substance of the allegations or defense strategy."

In an alleged plot that reads like a movie thriller, Headley is accused of spending two years casing outMumbai, even taking boat tours around the city's harbor to scope out landing sites for the attackers, who killed 166 people including six Americans.

The Washington-born son of a former Pakistani diplomat and an American mother, Headley changed his name from Daood Gilani in 2006 so he could "present himself in India as an American who was neither Muslim nor Pakistani," charging documents said.

Headley allegedly told investigators he had been working with the Islamist group Lashkar-e-Taiba (LeT) since 2002.

Indian media have reported that during his five lengthy trips to Mumbai Headley befriended Bollywood stars and developed a reputation as a fitness fanatic while staying in an expat enclave in south Mumbai near the US consulate.

Indian security analysts believe he could be the vital missing link in the bloody 60-hour siege which began onNovember 26, 2008.

The question about whether the 10 heavily-armed gunmen had specialist help to land undetected by sea and strike their targets with such precision has been posed ever since the attacks.

India and Washington blamed the deadly rampage on Pakistan's banned militant group LeT. The attacks stalled a fragile four-year peace process between the two nuclear-armed south Asian rivals.

Charging documents also indicated Headley was so eager to kill a Danish cartoonist and editor that he began working seriously on that plot two months before the Mumbai attacks.

Jyllands-Posten, Denmark's highest circulating daily, triggered a furor in the Muslim world by publishing 12 cartoons of Prophet Mohammed in 2005.

Headley allegedly told prosecutors he pretended to be interested in buying ads in the newspaper so he could tour the offices in Copenhagen and Arhus "in preparation for an attack," charging documents said.

Prosecutors say he was arrested at Chicago's O'Hare airport as he was on his way to deliver 13 surveillance videos to an Al-Qaeda-linked terrorist group in Pakistan called Harakat-ul-Jihad-Islami which was to carry out the attack.

Headley was initially charged only in the Danish plot, along with Tahawwur Hussain Rana, a former schoolmate who owns the Chicago-based First World Immigration Services that Headley allegedly used as a cover.

US justice officials released a raft of new charges related to the Mumbai attacks on Monday.

Headley faces six counts of conspiracy to bomb public places in India, murder and maim persons in India and Denmark, provide material support to foreign terrorist plots, and provide material support to Lashkar.

He was also charged with six counts of aiding and abetting the murder of US citizens in India.

His lawyer said he was not aware of any request by Indian authorities to interview Headley or to extradite him to face charges in the Mumbai attacks.

A status hearing was set for January 12.