Pfizer reported revenues below estimates, with shares of the Dow component and pharmaceutical company falling in early New York trading.
Pfizer has been trying to acquire FTSE 100 rival AstraZeneca. Britain's opposition Labor party called for an inquiry into the potential takeover over the weekend, after AstraZeneca rejected Pfizer's £63 billion ($106 billion) bid.
Clashes broke out in six cities in eastern Ukraine over the weekend and pro-Russian forces stormed a police station in Odessa, freeing close to 70 activists that were being held. Russia has warned Ukraine of "catastrophic consequences" unless it halts military operations against the rebels.
The rising tensions overshadowed a better-than-expected U.S. jobs report released on Friday, which showed 288,000 jobs were created in April, with the jobless rate at 6.3 percent. Analysts had expected an addition of 210,000 jobs, with unemployment at 6.6 percent.
On Monday, investors will eye the ISM non-manufacturing index for April at 10 a.m. ET. This tracks monthly changes in the services sector. Analysts at Barclays expect the index to rise to 54.5, above the 50-mark which shows sector expansion.
"This would be consistent with the pickup in activity in the manufacturing ISM and suggest a solid start to service sector activity growth," said Barclays' Bill Diviney in a morning research note.
After the closing bell there will be numbers from AIG.