Northwest Airlines said Tuesday it will cut its capacity later this year by 3 percent to 4 percent because of high fuel prices. The reductions were deeper than those announced in April, though they are smaller than cuts announced by many other airlines. The airline said it will try to shrink its staff through voluntary means, but layoffs are possible, too. Northwest said it has not yet arrived at the number of positions it wants to eliminate. Northwest Chief Executive Doug Steenland said Northwest is aiming to match its capacity to customer demand as airfares increase. “We don't anticipate doing anything in addition, but if fuel continues to be challenging we clearly have the wherewithal to take additional action,” he told analysts at a conference on Tuesday. Still, Steenland acknowledged that even the cuts announced Tuesday would not get Northwest to its profit goals. Northwest Airlines Corp. said it expects to reduce mainline flying by as much as 9.5 percent compared with a year ago. Domestic flying, including regional carriers, is now slated to go down by 7 percent to 8 percent. The cuts are expected to take effect in the fourth quarter, which begins in October.