The American Red Cross struggled on Friday to reassure beleaguered New York City residents that its disaster-relief efforts were at last getting up to speed, after the agency’s delayed arrival in devastated areas of Staten Island, Brooklyn and Queens drew intense criticism.

As of Friday, the Red Cross said, 25 of its emergency response vehicles — retrofitted ambulances each carrying 2,000 pounds of water, meals and snacks — had begun making their way through the hardest hit parts of the five boroughs. More were on the way, the agency promised.

The Red Cross had not yet opened the three temporary mobile kitchens that it announced on Thursday would be set up on Staten Island, in Riis Park in the Rockaways, and at the Aqueduct racetrack in Queens, the agency confirmed. The kitchens, which can produce 10,000 meals a day, would begin operating by Saturday, it said.

The organization’s response to Hurricane Sandy came under fire from public officials and volunteers, beginning with a televised tirade on Thursday by James P. Molinaro, the Staten Island borough president; he called the agency’s apparent absence from the relief effort an “absolute disgrace” and called on residents to stop donating money to the Red Cross.