Details of a cyanide threat against Tiger Woods and the 2001 New Zealand Open revealed

A former US special agent has revealed that he protected professional golfer Tiger Woods from a terrorism threat in New Zealand.

A cyanide-laced letter, which was delivered to the United States Embassy in Wellington in December 2001, threatened terrorist action against the New Zealand Golf Open, due to take place the following month with Woods attending.

Woods was playing in the 2002 New Zealand open as a favour to his kiwi caddie, Steve Williams.

Former special agent for the United States Department of State Diplomatic Security Service (DSS), Robert Starnes, held security responsibilities for the US missions in Wellington, Auckland, Christchurch and Apia, with all threat letters passing through his office for assessment.

In his new book, Dictators and Diplomats: A Special Agent's Memoirs and Musings, Starnes wrote about his experience's and revealed what was so concerning about the letter.

"The letter claimed suicide attacks could be expected against Tiger Woods and New Zealand citizens via fire bombings, train derailments, and poisoning the tournament's spectators," Starnes told Stuff.

"The author finished the letter by saying, 'If you don't believe what I'm saying, go ahead and put the contents of this sugar packet in your coffee'."

Starnes sent the substance to the New Zealand police and was called in for an urgent meeting a few days later.

A scientist working for the New Zealand police revealed that the substance in the sugar packet had tested positive for lab-grade potassium cyanide.

Starnes said that the author of the threatening letter outlined a view that New Zealand's security for the tournament was relaxed, and said that Woods represented US suppression and the exploitation of the Islamic people of Southeast Asia.

The author also claimed to be "an enemy of America, the Great Satan, as well as the Israeli regime and claimed allegiance to Islamic Jihad", Starnes said.

"This letter's ramblings included the opinion that America had not learned its lesson from 9/11 and he basically accused America's foreign policy of suppressing the weak."

Starnes said that the specific mention of a desire to orchestrate suicide attacks and violence against both Tiger Woods and New Zealand citizens resulted in major security concerns for both the New Zealand and United States government.

The government then asked the US Embassy not to go public about the threat letter.

"From a law enforcement perspective, I completely understood the importance of holding the information close so as not to telegraph or compromise their investigation and security plans to the letter's author," Starnes said.

New Zealand police tightened security at the golf open at Paraparaumu, north of Wellington, and warned the public to be vigilant against food and drink tampering, but were not more specific.

Other letters referencing a cyanide attack were sent to the New Zealand Herald in the same year.