The US Environmental Protection Agency (EPA) is today expected to unveil controversial new plans designed to curb emissions from US power plants and industrial facilities.

According to various reports, the agency intends to set out a timeline for introducing new greenhouse gas emissions standards for power plants by July and for oil refineries by December next year.

A source told The New York Times that the rules are likely to place a binding limit on the amount of carbon dioxide a power plant can emit per megawatt hour of electricity it produces.

Depending on the level at which the new emission standards are set, the rules could effectively outlaw the dirtiest coal-fired power plants and force energy firms to increase investment in cleaner gas and renewable energy sources.

The proposals will prove highly controversial and are already under fire from Republicans and industry groups, many of which have launched legal actions against the EPA challenging its right to regulate greenhouse gas emissions.

Republicans have also pledged to use their control of the House of Representatives to try to curb the EPA’s powers.

Speculation is mounting that they could use a partial-year spending bill that has to pass in early 2011 to avoid a government shutdown to try and secure concessions from the Obama administration that would limit the EPA’s authority.

The announcement comes as the EPA this week stepped up its battle with Texas over the introduction on 2 January of new rules requiring carbon intensive power plants and industrial sites to obtain permits guaranteeing that they use the most efficient technologies when undertaking upgrades or building new facilities.

Texas and over a dozen other states are suing the EPA in an attempt to overturn the new rules. However, Texas is the only state to refuse to implement the permitting regime when it comes into effect next month.

As a result, EPA assistant administrator for air issues Gina McCarthy wrote to state environmental officials this week warning that the agency would take over the operation of the permitting scheme.

“The unwillingness of Texas state officials to implement this portion of the federal programme leaves the EPA no choice but to resume its role as the permitting authority,” she wrote.

The move puts the Obama administration on a collision course with Texas Republican governor Rick Perry, who has consistently opposed the EPA and has argued that the new rules should be ditched on economic grounds.

A spokeswoman for Perry told reporters that the EPA’s rules “paint a huge target on the backs of Texas agriculture and energy producers by implementing unnecessary, burdensome mandates”.

In related news, the EPA secured victory this week in its legal battle with a coalition of oil companies and refiners over its decision to impose ethanol targets for gasoline sales.

A federal appeals court rejected the oil industry suit, which argued that the EPA had imposed the ethanol standards retrospectively after waiting until March to announce targets for 2010.

The court said in its ruling that oil firms had sufficient time to meet the renewable fuel standard, which requires that biofuels make up 8.25 per cent of gasoline sales this year.

Charles Drevna, president of the National Petroleum Refiners Association, expressed disappointment at the decision.

“This retroactive regulation by a federal agency establishes a deeply troubling and potentially far-reaching precedent,” he said in a statement.

“We are disappointed that the court did not overturn what is clearly a flawed and misguided approach toward implementation of the federal renewable fuels standard.”