A senior official responsible for overseeing rebuilding efforts in Iraq said yesterday that spending on construction has surged in recent weeks, despite continuing security problems that have kept Iraqi workers away from the job.

At a Pentagon briefing, David Nash, a retired admiral managing the spending of U.S. tax dollars, said more than $4 billion has been obligated to specific projects, about double the amounts reported two months ago.

The upbeat assessment came just weeks after the Pentagon and the U.S.-led occupation authority in Iraq were stung by criticism from lawmakers that little of the $18.4 billion allocated by Congress for the effort last year had been spent.

Nash said yesterday that at one point in recent months only about a quarter of the Iraqis working on reconstruction were showing up because of the continuing violence in the country. "Yes, it's had an impact on how many people show up to work," Nash said. "Security is having an impact on us."

But he said that more than 8,000 Iraqis, three-quarters of those scheduled, arrive for work daily and that the work is accelerating.

Some Americans and other Westerners working for U.S. contractors left Iraq over the past several weeks because of the deteriorating security situation, he said. "The contractors have showed up with great vim and vigor, and in fact they're at work," Nash said during a half-hour briefing. "So things are going very well."

He said authorities are "putting in place" up to $75 million in new construction projects every week. Briefing documents from his Program Management Office show that about $3 billion was obligated to construction projects by the end of last week, compared with about half that amount a month ago. Spending has been heaviest on electricity and water projects.

Critics acknowledged some improvements in the reconstruction effort, including the delivery of electricity and fresh water to Iraqis. But they said yesterday's briefing appeared oriented to create a favorable impression in the weeks leading up to the handover of limited authority to an Iraqi government on June 30 and in the months leading up to the U.S. presidential election.

"They're clearly trying to put the best face on this," said Tim Rieser, chief Democratic clerk for the Senate Appropriations foreign operations subcommittee, which is monitoring the spending. "Yet by any objective measure they're falling far short of what they said they were going to do when they asked for all this money."

The coalition had planned on spending nearly $8 billion through March.

Sen. Patrick J. Leahy (D-Vt.), the subcommittee's ranking Democratic member, said the future of reconstruction efforts hangs in the balance because the country remains so dangerous and many contractors and Iraqis are still afraid to work.

"Security is quickly becoming the X-factor that is impeding and complicating the reconstruction effort," Leahy said in a statement. "Many people predicted these problems back when the Administration made its request for far more money than it could effectively spend. The reality on the ground is illustrative of the many needless mistakes that have created the mess we face today."

Nash said he is "very enthusiastic, very positive" about the overall direction of reconstruction. He estimated that $5 billion worth of projects will be underway by July 1, when Iraqis are scheduled to be largely in control of the country.

Chris Ward of Halliburton Co.'s engineering and construction unit, KBR, spoke at a job fair in Wichita Falls, Tex., on May 1 to try to recruit workers for Iraq.