Crude prices edged up after seesawing on Tuesday as U.S. service sector data came in supportive, but weak European data deepened demand concerns.

The Institute for Supply Management reported that U.S. non- manufacturing index registered 53.7 percent in May, 0.2 percentage point higher than the 53.5 percent in April. It was the 29th straight month of expansion, offering supports to crude markets.

Besides, the investors were awaiting the results of conference call held on Tuesday by finance ministers and central bank governors of the Group of Seven leading industrialized nations, which was set to discuss the European debt crisis, trying to figure out some way to prevent the problems from further worsening.

And amid severe markets declines, the hopes for more monetary stimulus rose. Markets were awaiting the Federal Reserve's report later in the week, hoping the central bank would give some hints about the third round of quantitative easing policy (QE3).

But in Europe, weak data kept deepening concerns about global oil demand growth. Euro zone retail sales fell more than expected in April. Purchasing managers indexes from Markit showed the major economies in the region were seeing declines at differed grades and the vast private economy contracted in May at the fastest pace in nearly three years.

The more international pricing benchmark of Brent crude edged down after choppy trading. And its trading volume was also lower than U.S. crude. But volume of both Brent and U.S. WTI were under their 30-day averages.

Light, sweet crude for July delivery rose 31 cents, or 0.37 percent to settle at 84.29 dollars a barrel on the New York Mercantile Exchange. In London, Brent crude for July delivery slipped 1 cent to close at 98.84 dollars a barrel.