The Dow was set to make triple-digit gains after two opinion polls released over the weekend showed those wanting to stay in the European Union holding a slim majority against the leave campaign. Dow futures were up about 200 points, while S&P and Nasdaq futures advanced 23 points and 57 points, respectively.
Investors have been on edge in the run-up to Britain's June 23 referendum.
Investors this week area also keeping an eye on the Federal Reserve, with Janet Yellen set to testify in front of the U.S. Senate Committee on Banking, Housing and Urban affairs on Tuesday, and the House of Representatives' Committee on Financial services on Wednesday.
Meanwhile, Minneapolis Fed President Neel Kashkari will take part in a panel discussion in Washington, D.C. to take part in the Third Symposium on Ending Too Big To Fail from 12:15 p.m. ET.
No major earnings are expected.
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