Sales at U.S. chain stores finished the month showing surprising strength, with retailers looking forward to a busy spring season, a report said on Tuesday. The pace of sales at major retailers increased by 5.8 percent on a year-over-year basis for the week ended Feb. 28, up slightly from the preceding week's 5.6 percent pace, research group Redbook said. Sales in February were up 1.2 percent compared with January. "The strength surprised some retailers, since it was not entirely typical of a transitional month early in a new season," the report said Redbook expects March chain store sales to stay flat with February's 5.7 percent rise on a year-over-year basis. The Redbook data are compiled from a sample of same-store sales at general merchandise retailers representing about 9,000 stores. Same-store sales measure revenue at stores open at least one year.////