WASHINGTON (AP) — Americans stepped up purchases of new homes in August after cutting back in July, suggesting that higher mortgage rates are not yet slowing the housing recovery.Sales of new homes increased 7.9 percent last month to a seasonally adjusted annual rate of 421,000, the Commerce Department said Wednesday. That comes after sales plunged 14.1 percent in July to a 390,000 annual rate.The rebound in sales could ease worries that higher mortgage rates have started to dampen sales. It coincided with the best month of sales for previously occupied homes in more than six years.