O'Brien will be accompanied by former minister Brian Wilson, who now acts as Prime Minister Tony Blair's special representative for trade and reconstruction in Iraq.
"They will be pressing the case for British firms in the reconstruction work in Iraq," a government official said, referring to their visit to the US next week.
The Guardian newspaper on Friday published what it said were leaked documents indicating frustration within Blair's government about the way contracts had been handed out.
UK firms had hoped Britain's role as the United States' main ally in the war would ensure them work. But few have won high-profile primary contracts so far.
"All ministers in the government who are in frequent touch with their US opposite numbers (need) to ensure that the US administration are in no doubt about the political importance we attach to UK firms being seen to contribute actively to the
reconstruction process," the paper quoted O'Brien as saying in one document.
Last month, Britain's largest engineering services firm Amec failed, in a joint venture with Fluor of the United States, to win a US contract worth up to $1.2 billion to refurbish Iraq's oil industry.
"Everybody understands the rules of engagement"
special representative, trade and
reconstruction in Iraq
Two contracts to rebuild Iraqi oilfields worth a total of $2 billion went to a unit of US Vice President Dick Cheney's old firm, Halliburton, and US construction giant Parsons which teamed up with Worley Group of Australia.
Then, Wilson said the decision was not entirely surprising, but there was more work to compete for. "Everybody understands the rules of engagement and it is not easy for non-US companies to succeed at that level of contract," he said.
The United States is spending far more than any other country on rebuilding Iraq's infrastructure and is racing to allocate $18.6 billion worth of construction and rebuilding projects before a planned 1 July handover of power to the Iraqis.