Passers-by are reflected on a stock quotation board at a brokerage in Tokyo, Sept. 29, 2015. Reuters

Asian stocks were mixed Tuesday morning after U.S. indexes slipped Monday, dragged down in part by questions over the Pfizer-Allergan merger. Tokyo stocks were slightly lower as trading resumed after a Monday holiday.

Australian stocks fell as well, as metal prices declined. Big miners like BHP Billiton and Rio Tinto both fell by more than 1 percent.

New Zealand's market, however, added another 0.4 percent, extending gains that started a week ago. Futures for Hong Kong, which hasn't opened yet, pointed higher.

In New York, the Dow Jones Industrial Average fell 0.17 percent and the S&P 500 0.12 percent Monday as trading thinned ahead of the Thanksgiving holiday. Pfizer dropped 2.6 percent and Allergan 3.4 percent after the drug companies announced their $160 billion merger. Investors are disappointed with the amount of savings the merger will generate and wary of possible antitrust issues and the possible resulting delay in Pfizer's plan to break up into two companies, Reuters reported, citing analysts.