* Pfizer drops as quarterly revenue misses estimates
* Fed begins two-day policy meeting
* Oil slips on worries about Iran sanction
* Futures down: Dow 0.13 pct, S&P 0.04 pct, Nasdaq 0.08 pct (Adds comments, details, updates prices)
By Sruthi Shankar
May 1 (Reuters) - U.S. stock index futures were down slightly on Tuesday after disappointing results from Pfizer, while investor concerns about inflation, rising costs and protectionist policies continued.
At 8:45 a.m. ET, Dow e-minis were down 31 points, or 0.13 percent. S&P 500 e-minis were down 1 points, or 0.04 percent and Nasdaq 100 e-minis were down 5.5 points, or 0.08 percent.
Trading volumes could remain light as most financial centers across Europe and Asia were closed on account of May Day.
U.S. equity index futures got some reprieve overnight after President Donald Trump postponed the imposition of steel and aluminum tariffs on Canada, the European Union and Mexico until June 1, and reached agreements for permanent exemptions for Argentina, Australia and Brazil.
The decision comes ahead of Treasury Secretary Steven Mnuchin's highly anticipated trip to China later this week to discuss trade issues.
"You had the tariff news, but that may have already been baked in," said Scott Brown, chief economist at Raymond James in St. Petersburg, Florida.
"It causes the same amount of uncertainty, you had worse-than-expected revenue from Pfizer, and there might be some caution ahead of Apple results."
Pfizer fell 1.3 percent after the largest U.S. drugmaker's quarterly revenue missed estimates. Merck shares also dipped 1.1 percent despite profit beating estimates and the company lifting earnings forecast for the year.
Apple, the world's biggest publicly traded company, comes out with results after market closes on Tuesday. All eyes will be on the earnings report as recent warnings from some chipmakers, on softening demand for iPhones and other top-end models, took a toll on Apple's shares.
The U.S. Federal Reserve begins its two-day monetary policy meeting on Tuesday. Although no change in policy rates is expected, investors will watch for clues on whether three more rate hikes are due for the rest of 2018.
A rally in oil and other commodity prices have raised fears about higher raw material costs. Some companies, including Caterpillar and Procter & Gamble, have flagged such concerns this earnings season.
Oil prices which are near 2014 highs, surged on Monday after Israeli Prime Minister Benjamin Netanyahu presented what he called evidence of a secret Iranian nuclear weapons program.
The prices were slightly down on Tuesday on worries that Trump would pull out of the Iran nuclear deal. (Reporting by Sruthi Shankar in Bengaluru; Editing by Shounak Dasgupta)