WASHINGTON - With a critical Senate committee vote on healthcare reform looming, President Barack Obama on Saturday urged lawmakers to unite behind the effort but Republicans warned the plan would slap a hefty tax on many Americans.

Obama, who has made reform of the $2.5 trillion U.S. healthcare system his top domestic priority, said in his weekly radio and Internet address the push for change was gathering momentum with the completion of the Senate Finance Committee's legislation.

The panel is due to vote on its healthcare reform plan on Tuesday after months of bipartisan work but it was unclear whether the final product in the Democratic-controlled committee would win the backing of any Republicans.

The committee is the last of several panels in the Senate and the House of Representatives to consider a healthcare reform bill. Once the panel votes on the measure, it will be combined with another Senate healthcare bill before moving to a vote in the full chamber.

Obama hailed the Finance Committee bill, noting the Congressional Budget Office had concluded the legislation would make health insurance coverage affordable to millions of Americans who do not have it and would slow the growth of healthcare costs.

The CBO estimated the cost of the program at $829 billion over 10 years, below Obama's $900 billion goal, and said it had program cuts and revenue plans that would achieve the president's aim of not adding to the deficit.

This is another milestone on what has been a long, hard road toward health insurance reform, Obama said in his address. The approach that is emerging includes the best ideas from Republicans and Democrats, and people across the political spectrum.

REPUBLICAN CRITICISM

But Republicans criticized the plan in their weekly radio address, saying Obama was moving too fast, the measure would cost too much and it would impose hefty new taxes on many ordinary Americans.

We in the Congress have a duty to tackle this problem, but the solution we settle upon should not be rushed, and the solution should not be worse than the problem we are trying to solve, Senator George LeMieux said in the address.

LeMieux said the plan being pushed by Obama and Democratic lawmakers would place a big financial burden on state governments and would require all adults to buy insurance or pay a $750 penalty.

The president says this isn't a tax. I don't buy it, he said. The penalty is paid directly to the IRS (Internal Revenue Service) when you pay your taxes, and it's certainly not optional.

If it looks like a tax, and it's paid like a tax, then it is a tax, plain and simple, LeMieux said.

Lacking Republican support in Congress, Obama pointed to Republicans elsewhere who have backed reform, from New York Mayor Michael Bloomberg to California Governor Arnold Schwarzenegger and former Senate Majority Leader Bill Frist, a heart surgeon.

That future is within our grasp, he said. So, let's go finish the job.

(Editing by Mohammad Zargham)