A retired British businessman on Friday lost a High Court battle against extradition to the United States on charges of conspiring to sell missile parts to Iran.

Christopher Tappin, 64, denies attempting to unlawfully export batteries for surface-to-air missiles, which were to be shipped from the United States to Tehran via the Netherlands.

Two judges sitting at the High Court in London ruled that his arguments that he had been entrapped by US agents were "unsustainable", and also denied that it would be "oppressive" to extradite him.

The businessman has fought a long battle against extradition to the United States, where he could face 35 years in jail.

He was appealing against a ruling by a lower British court in February 2011 that said he could be extradited, a decision that was also approved by the interior minister, Theresa May.

Tappin says he was unaware that batteries he had sourced in the United States were destined for Iran, in violation of US export laws, and says he was caught up in a US customs sting.

He has said he believed he was exporting batteries for the car industry in the Netherlands, although US authorities say he also told customs officials his shipments were destined for an oil company in Norway.

Tappin's lawyer Edward Fitzgerald told the High Court in December that US Federal Bureau of Investigation (FBI) agents, using the cover of a fictitious export company, set out to "dupe, deceive and ensnare" the businessman.

But the judges on Friday rejected this argument, and in their written ruling said: "From the outset it is evident that there was no lack of predisposition on the appellants part to engage in the criminal conduct."

Tappin, the president of a golf club in Kent in an upscale area southeast of London, said he was "thoroughly disappointed" at the judgement.

His lawyers said they would try to take the case to the Supreme Court.

"I was relying on the British justice system to protect me from false allegations made by a maverick government agency clearly operating outside the law in the US," Tappin told reporters.

"Our extradition laws completely fail to prevent such improper extraditions."

He said he feared for the impact of the decision on his family, including his wife, who has a debilitating illness and for whom he helps care.

"I'll now consider all my options and do what I can to bring an end to this nightmare," he added.

His lawyers, Kaim Todner Solicitors, also condemned the extradition treaty and said: "We will now be lodging an application to certify a point of law of public importance to take this case to the Supreme Court."

The Supreme Court in London will only take on cases if it believes there is an important, wider point of law at stake.