A US hostage in Iraq has appeared on a video tape urging his government to "open a dialogue with the Iraqi resistance" to save his life.
The hostage was identified as a kidnapped subcontractor
The hostage is believed to be Jeffrey Ake, a subcontractor who went missing on Monday, say US officials.
US Secretary of State Condoleezza Rice said they were working "very, very hard" to secure his release but they would not negotiate with his captors.
No group has claimed responsibility for the abduction.
Unlike in previous videos of hostages, there was no banner giving the name of the kidnappers.
In the video, shown on al-Jazeera satellite television, the hostage sits behind a desk with three armed and masked men standing beside him.
He is holding up his passport and driving licence.
"I ask my family and friends to demonstrate and speak directly to the American government to open a dialogue with the Iraqi resistance," he says in the video.
Mr Ake was abducted by eight hooded men who drove up in two cars to the construction site near Taji, north of Baghdad, a security source was quoted by the AFP news agency as saying.
"They overran the meagre security at the site, went right to him and took him. They could have been observing him, he could have been betrayed by someone there," said the source, who asked not to be named.
Ms Rice told a news conference they would be continuing with their policy of not negotiating with terrorists as "it only encourages them".
"It is our great hope that working with those who have information we can resolve this in a way that is successful, and that means in protecting the life of the hostage.
"We are thoroughly engaged with the Iraqis, and with others, in trying to do this," she said.
More than 150 foreigners have been kidnapped in Iraq in the past year, either by insurgents fighting foreign troops or by criminals seeking ransom.