US President Barack Obama's Senate allies launched a three-day push Tuesday for sweeping legislation to battle climate change, with time running short before a high-stakes global summit in December.

And Obama, signaling that he will not wait for lawmakers to act, planned to unveil the largest modernization of the US electricity grid in history, in a 3.4-billion-dollar bid to unleash a new era of renewable energy consumption.

Some 100 firms, manufacturers, utilities and cities will get awards worth from 400,000 to 200 million dollars to help build a nationwide "smart energy grid" to cut costs and improve reliability of the creaking system.

While Obama unveils the plan in Florida, his secretaries of energy, interior and transportation, as well as his Environmental Protection Agency chief, will urge senators to act quickly to curb pollutants blamed for global warming.

The administration heavy-hitters will appear before the Senate's Environment and Public Works Committee as it opens three days of hearings on legislation written by Obama's Democratic allies to fight climate change.

Democratic Senator John Kerry, a key sponsor of the legislation, will be the first witness before the panel, which is run by the bill's other main sponsor, Democratic Senator Barbara Boxer.

Obama has said he wants to make as much progress as possible to reassure skeptics at December global talks in Denmark's capital Copenhagen that the United States is pressing ahead with aggressive climate change remedies.

But aides have already warned that the legislation will not pass before the UN climate change conference -- a delay that could cripple hopes of a major new international treaty.

The US House of Representatives approved a so-called "cap and trade" emissions regime in June, and the Senate is now poised to take up the measure with a new poll showing nearly six in 10 Americans support such a plan.

Under the expected cap-and-trade regime, the government would set the total level of domestic emissions allowable and then allocate quotas to companies.

Firms that emit less than their quota would be allowed to sell their surplus allocation to others that exceed theirs. Those in excess could also face fines.

The House bill calls for cutting US greenhouse gas emissions by 17 percent from 2005 levels by 2020 and by 83 percent by 2050. The Senate's slightly more ambitious bill calls for a 20-percent cut by 2020.

The Senate text also makes a push for nuclear energy research and training, and promotes natural gas as a clean energy source.

"Our bill is the best way to proceed. It provides flexibility to businesses and powerful incentives to drive innovation. It helps consumers, workers, agriculture, transportation, energy efficiency, wildlife, cities, counties, and it will launch an economic transformation," Boxer said Tuesday.

About sixty percent of respondents to a CNN/Opinion Research Corporation survey said they favor such an approach, while 37 percent said they oppose it. The survey's error margin was plus or minus three percentage points.

Obama's Republican foes have mostly rejected the administration's approach, with some warning it would inflict severe economic pain on traditional industries as the US economy makes the transition to cleaner energy.

Obama on Friday hit out at "naysayers" who peddle "cynical" claims that global warming is a myth and warned that "the closer we get, the harder the opposition will fight.

Obama argued that the fight against climate change was not just necessary for the health of the planet, but should also spur a new range of green jobs and technologies that could unleash economic growth and promote energy independence.