A Singapore judge on Friday allowed the extradition to the United States of four Singaporeans accused of illegally selling US-made radio components to Iran that ended up in Iraqi roadside bombs.

The judge ordered the four committed to prison pending an extradition order by Singapore Law Minister K. Shanmugam, who is also the foreign minister.

The US government immediately welcomed the decision even though the four electronics company employees, who strongly denied deliberately violating US laws, were given 15 days to contest the judge's ruling.

"This ruling reflects the strong spirit of cooperation between the United States and Singapore in combating transnational crime, including the illicit trade in arms and equipment that can pose significant threats to the United States and the international community," said US Ambassador David Adelman.

A US embassy statement said the four had been charged with violations of American laws relating to fraud involving the "unlawful export from the United States of military antennas and radio frequency modules".

The four suspects were all in the electronics parts distribution business when they were arrested in October and will be tried in a District of Columbia court if extradited.

"I have no doubt they will be accorded a fair trial by the US courts," District Court Judge Chia Wee Kiat said.

He said all the court needed was to "consider if there is a prima-facie case" and that this had been established during the hearings.

In court statements in December, Wong Yuh Lan, Lim Yong Nam, Lim Kow Seng and Hia Soo Gan Benson rejected US charges that they had conspired to evade a US trade embargo against Tehran.

They were arrested by Singapore police on US charges of illegally exporting US-made radio equipment to Iran including 6,000 radio modules and 55 antenna parts, some of which were found in bombs targeting coalition forces in Iraq.

The Singapore government turned over the US extradition request to a local court to determine the merits of the case.

"I really did not take part in any conspiracy... and I truly did not know that US origin goods were not allowed into Iran," Wong, the only woman among the four, said in a statement read out in court by her lawyer in December.

Wong, who was an office clerk for a company run by an Iranian who is now at large, said her incarceration during the hearings "has caused untold anguish to me, my family and my young children".

Wong's lawyer Ravinderpal Singh said: "I am going to look at the written judgement and decide on the next course of action with my client."

Hamidul Haq, the counsel for the three other accused, said he will lodge an appeal.

"There is a period of 15 days that Singapore has before extradition can take place," Haq told reporters.