WASHINGTON -- President Barack Obama defended the work of the Environmental Protection Agency on Tuesday, saying he would stand with the agency that has taken a beating from Republicans in Congress and on the presidential campaign trail for regulations that the GOP maintains will cripple the economy and kill jobs.

Obama, making his first-ever visit to the EPA, took issue with those claims, saying he does not buy the notion that there is a choice between clean air and clean water and a growing economy. He said the mission of the agency is "vital."

"That is a false debate. We don't have to choose between dirty air and dirty water or a growing economy. We can make sure that we are doing right by our environment and in fact putting people back to work all across America," Obama told about 800 EPA employees gathered at headquarters in Washington, reminding them that before Republican President Richard Nixon created the agency in 1970, rivers caught fire and were devoid of life.

"When I hear folks grumbling about environmental policy, you almost want to do a 'Back to the Future' reminder of folks of what happened when we didn't have a strong EPA," Obama said, adding, "You have a president who is grateful for your work and will stand with you every inch of the way."

Under Obama, the EPA helped draft a historic rise in fuel economy standards for new cars and trucks, issued the first-ever rules to curb mercury from the nation's coal-fired power plants and started regulating the heat-trapping gases blamed for global warming.

Yet, at times, Obama has had to scale back his aspirations on the environment in the face of a weak economy and political resistance.

The Republican takeover of the House in 2010 killed his campaign pledge to pass comprehensive legislation to address global warming. Since then, the House has passed a string of bills to block EPA rules, all of which have failed in the Democratic-led Senate and drawn a veto threat from the White House.

But the true low point for Obama on the environment came in September, when faced with criticism from industry and Republicans, he decided against strengthening a standard for the main ingredient in lung-damaging smog, going against the recommendation of agency scientists and EPA Administrator Lisa Jackson.

Obama redeemed himself in environmentalists' eyes late last year. First, he delayed a decision to build a pipeline to bring tar sands oil from Canada to the Texas Gulf Coast.

Then, in December, the EPA finalized the first-ever standards to control toxic mercury pollution from power plants, over the objections of Republicans and industry groups.

Now, in the midst of his re-election campaign, the big question is whether Obama will continue that trend.

Regulations to curb power plant pollution are still in the pipeline, including a much-anticipated proposal to control greenhouse gases from new power plants.

Meanwhile, Republican presidential hopefuls continue to criticize the agency's actions under Obama, saying its regulations have placed a massive burden on business and hindered economic growth.