The British government has lost a bid to extend the "unduly lenient" jail term given to a London dentist for planning to fight for the Taliban and "kill many" British and U.S. soldiers in Afghanistan.

Pakistan-born Sohail Qureshi was jailed for 4-1/2 years in January for preparing to commit attacks but Attorney General Patricia Scotland appealed, arguing the sentence was "unduly lenient".

However, London's Court of Appeal rejected that call on Tuesday, with senior judge Lord Nicholas Phillips saying that while the term was lenient it was "not unduly lenient".

He said links between Qureshi, described as a "Walter Mitty" fantasist character and acts of terrorism were "relatively remote".

Qureshi, 30, was arrested in October 2006 at Heathrow Airport as he prepared to fly to Pakistan with about 9,000 pounds ($17,780) in cash, medical supplies and night vision gear.

He pleaded guilty to preparing for the commission of terrorist acts, possessing an article for a terrorist purpose and possession of records likely to be useful in terrorism.

It was the first conviction under a 2006 law covering cases where suspects are preparing to commit an act of terrorism but fall short of having a concrete plan in place.

Prosecutors said he was a "dedicated supporter of Islamist extremism".

Police had found a posting he had made on a militant Web site referring to his Pakistan trip which read: "All I know is that it is a two or three-week operation. Pray that I will kill many, brother. Revenge, revenge, revenge."

Lawyers for the Attorney General had argued that the starting point for his sentence should have been between 10 and 16 years.

But Appeal Court judge Brian Barker said that while Qureshi had admitted "grave charges", the offences were at the lower end of the spectrum.

Qureshi will now walk free in about a year.