FACTBOX: Why are U.S. gasoline prices so high?

(Reuters) - Average nationwide U.S. gasoline pump prices jumped above $4.00 a gallon for the first time ever as record-high crude oil prices near $140 a barrel tricked down to the consumer level, U.S. government data showed on Monday.

Here are some questions and answers on why gasoline prices are so high, and what U.S. lawmakers want to do about it.

WHY ARE U.S. GASOLINE PRICES SO HIGH?

Crude oil prices -- which account for nearly 70 percent of the cost of gasoline at the pump -- jumped nearly 9 percent to a record $139 a barrel on Friday. Crude retreated on Monday but remained near $135 a barrel. Investment bank Morgan Stanley predicted $150-a-barrel crude by July 4, a U.S. holiday that falls during the heavy summer driving season.

Fuel refiners and marketers have passed only some of the increase in crude prices down to consumers at the pumps. With profit margins squeezed, refining companies like Valero Energy Corp have curtailed gasoline production until the price of gasoline rises relative to crude.

HOW ARE U.S. CONSUMERS REACTING?

U.S. drivers this summer are expected to cut gasoline use for the first time since 1991. U.S. government data showed highway miles driven in March down 4.3 percent from a year earlier, the first March decline since the oil shock of the late 1970s. Department of Transportation data showed Americans drove 11 billion miles less in March 2008 than they did a year earlier. Estimated travel on U.S. public roads had not fallen in March since 1979.

WHAT ARE U.S. POLITICIANS DOING ABOUT IT?

Democrats in the U.S. Senate will try again this week to advance legislation that would slap a new tax on oil company profits. Republicans in Congress have failed in recent attempts to advance a production-centered plan that includes opening an Alaska wildlife refuge to drilling and allowing coastal states to decide whether they want to allow drilling in their waters.

WHAT DO THE OIL COMPANIES SAY?

Oil companies like Exxon Mobil Corp. say high energy prices are not their fault but are due to soaring crude oil markets. They oppose efforts to raise taxes on their profits, saying higher taxes will make it harder for them to compete abroad with state-owned oil companies for shrinking energy resources. Oil companies say they bear some of the highest tax burdens - Exxon's effective tax rate is about 49 percent of revenues. The American Petroleum Institute answers complaints about windfall profits with statistics showing oil industry profits per dollar of revenue are in line with other industries, actually lagging some such as pharmaceuticals.

(Reporting by Chris Baltimore; Editing by David Gregorio)