President Barack Obama will attempt to kick-start a global climate agenda on Tuesday with proposals including a plan to limit carbon emissions from existing U.S. power plants that is sure to face opposition from the coal industry, many business groups and Republican lawmakers.

Obama, whose first-term attempt to reduce greenhouse gas emissions through a "cap and trade" system was thwarted by Congress, promised in his second inaugural address to tackle the issue again.

Environmentalists and Obama's political base have been anxious for action, but the first months of his second term have been dominated by immigration reform, a failed attempt to pass strict gun control measures, and a series of political scandals.

Republicans, in turn, have been emboldened by Obama's stumbles. Many also question climate science and oppose regulatory actions they say could hurt the economy.

The Democratic president aims to address those concerns and make good on his inaugural promise with a speech, scheduled for 1:55 p.m., that lays out a new plan to reduce emissions, boost renewable fuels, and lead the world in tackling global warming.

The key proposal involves the thousands of power plants, many of them coal-fired, which account for roughly one-third of U.S. greenhouse gas emissions.

Obama will direct the Environmental Protection Agency to draft a plan setting carbon emission limits on existing power plants by June 2014, finalizing those rules a year later, according to senior administration officials who briefed reporters before the speech.

"We already set limits for arsenic, mercury and lead, but we let power plants release as much carbon pollution as they want," one official said.

The proposals are likely to draw criticism from segments of the energy industry and some Republican lawmakers that they will cost jobs and hurt the U.S. economic recovery. In addition, they could be tied up in court for years.

The administration officials did not give details of what the limits for existing plants would entail. Separately, the EPA would finalize overdue plans for carbon limits on new power plants by September, they said.

Environmental groups that had early word of the administration's plans cheered.

"Tackling carbon pollution from power plants is the greatest opportunity and should be at the core of any serious approach to reduce U.S. emissions. For the first time, a U.S. president is taking such action," Andrew Steer, president of the World Resources Institute, said in a statement.

"This announcement will have ripple effects that will increase the urgency of action around the globe."

KEYSTONE OVERHANG, INTERNATIONAL FOCUS

None of the president's proposals, including plans to reduce emissions from heavy duty trucks after 2018, require congressional approval. That alone is likely to spark howls from Obama's opponents on Capitol Hill.

"(Obama) made it very clear that his preference would be for Congress to act and move comprehensive energy and climate legislation forward," the official told reporters. "At this point ... the president is prepared to act."

Some environmentalists fear that Obama will use new climate measures to head off criticism if his administration approves the proposed Keystone XL pipeline, which would carry oil from Canada to refineries in Texas.

A senior administration official said the decision on Keystone has not been made.

Green groups want Obama to reject the pipeline. Republicans and many businesses say it will help the economy, and some unions support the project because of the jobs likely to be created during the pipeline's construction.

The president's allies abroad will be watching, too. In 2009, Obama pledged to reduce U.S. greenhouse gas emissions by roughly 17 percent below 2005 levels by 2020 - cheering partners in Europe, who were frustrated by less ambitious promises made by Obama's Republican predecessor, George W. Bush.

Obama will stand by that pledge on Tuesday, and officials said Washington wants to take the lead in international efforts to seek a new agreement to reduce emissions after 2020.

"We will be seeking an agreement that is ambitious, inclusive and flexible," the White House said in a written version of Obama's climate plan.

As part of its global efforts, the White House would propose World Trade Organization talks on free trade in environmental goods and services, officials said. The United States would also plan to end its support of public financing for new coal power plants overseas unless they used carbon capture technology. Very poor countries would still get support.

Obama and Chinese President Xi Jinping agreed this month to cooperate in fighting climate change by cutting the use of hydrofluorocarbons, or HFCs.

The White House plan includes measures to tackle HFCs as well as emissions from methane, another potent greenhouse gas.