EL PASO, Texas—A British businessman was set to change his plea Thursday over allegations that he tried to buy missile parts from undercover U.S. Agents and illegally sell them to Iran.

Karen Todner said she hoped the plea deal would allow her client, Christopher Tappin, to return to Britain soon to be with his family. The details of the plea were being made public Thursday in federal court in Texas.

“The odds are so heavily stacked against a defendant who chooses to plead not guilty and then is subsequently found guilty that the vast majority of people facing trial in the U.S. opt to take a plea agreement,” Todner, Tappin’s British attorney, said in an email last week.

Tappin, 65, had pleaded not guilty to various export charges after his extradition from the United Kingdom in February. He has been free on bond since April and was scheduled for trial Monday.

He is accused of giving the undercover agents false documents to circumvent the requirement for defense articles to be licensed prior to being exported.

“From the moment Chris was put on a plane all we ever wanted was his swift and safe return,” said Tappin’s wife, Elaine Tappin. “However upsetting, this is the beginning of that process.”

Tappinwas extradited on charges of conspiracy to illegally export defense articles, aiding and abetting the illegal export of defense articles and conspiracy to conduct illegal financial transactions. The most serious of those charges is punishable by up to 20 years in federal prison.

The retired British businessman has been living in an upscale Houston neighborhood since his release on a $1 million bond in April.

A federal indictment filed in 2007 said a cooperating defendant provided computer files showing Tappin intended to send surface-to-air-missile batteries to a Tehran-based company and that Tappin and the cooperating defendant had illegally sold U.S. technology to Iran in the past.

The U.S. government alleged Tappin provided undercover agents with false documents to deceive authorities and circumvent the requirement for the batteries to be licensed by the government before being exported.

Tappin’s extradition in February touched a nerve in Britain, where many view the fast-track extradition arrangements between the U.K. and the U.S. as unfairly weighted in Washington’s favor.

He fought his extradition for two years until being denied a petition to take the case to Britain’s Supreme Court. After he was brought to Texas, Tappin was held for about two months at the Otero County Jail, where he initially was put in solitary confinement at his request.

Two men have already been sentenced to prison for charges stemming from the indictment. Robert Gibson, another British national, pleaded guilty in April 2007 and was sentenced to 24 months in prison. Robert Caldwell, from Oregon, was found guilty in July of that year and received a sentence of 20 months.