FACTBOX: U.S. presidential candidates on environment, energy

(Reuters) - With crude oil prices hovering near a record $135 a barrel, energy and environmental issues like global warming have moved to the forefront of the U.S. presidential campaign.

Here is what Republican John McCain and Democrat Barack Obama, who is close to capturing his party's nomination, are saying saying about energy and the environment:

CLIMATE CHANGE

Obama would cut carbon dioxide (CO2) emissions to 80 percent below 1990 levels by 2050, reduce emissions to 1990 levels by 2020 and require fuel suppliers to cut carbon content by 10 percent by 2020.

McCain favors a cap-and-trade CO2 approach. He sponsored legislation in 2007 to cut emissions by 30 percent by 2050.

GASOLINE PRICES

Obama would probe energy industry activities and stop filling emergency oil reserve.

McCain would suspend federal gasoline tax from May 22 to September 1 and suspend filling oil reserve.

OIL USE

Obama would reduce overall U.S. oil consumption by at least 35 percent, or 10 million barrels per day, by 2030 to offset imports from OPEC nations.

McCain has set no specified targets. He has said he will unveil a strategy to reduce reliance on foreign oil sources.

VEHICLE FUEL ECONOMY

Obama would double fuel economy standards in 18 years, give automakers tax credits to retool plants and invest in advanced lightweight materials and new engines.

McCain has not specified CAFE targets. He voted against energy amendments in 2003 that would have boosted CAFE to 40 mpg

by 2015.

BIOFUELS

Obama would boost the renewable fuel standard to at least 60 billion gallons of advanced biofuels like cellulosic ethanol by 2030; build out ethanol distribution infrastructure; mandate that all new vehicles be "flexfuel" by the end of 2012; and produce 2 billion gallons of "cellulosic" ethanol from non-corn sources like switchgrass by 2013.

McCain favors ethanol incentives after opposing them in the past. He generally opposes subsidies and tariffs that distort marketplace.

(Compiled by Chris Baltimore)