Stock futures tumbled Sunday night to kick off a new trading month, as investors weighed new U.S. tariffs on goods from key trade partners and their potential impact on the economy and corporate profits.

The Hang Seng China Enterprises Index dropped as much as 2.2% in early trading, in line with declines across the region. Hong Kong’s stock market has been shut since midday Jan. 28 while equities on the mainland will start trading again on February 5.