(Adds comments by Cantor, Pelosi and size of vote)
By David Morgan and Thomas Ferraro
WASHINGTON, March 5 (Reuters) - The Republican-led U.S. House of Representatives voted on Wednesday to delay for one year the tax penalty Americans will pay under President Barack Obama's healthcare law if they decline to enroll in health coverage.
The vote, part of a Republican election-year attack strategy against the 2010 healthcare law known as Obamacare, marked the 50th time House Republicans had passed legislation to try to repeal or dismantle it.
The measure to delay the tax penalty passed by a vote of 250-160, with 27 Democrats joining with 223 Republicans to back the legislation. The bill is certain to go nowhere in the Democratic-controlled Senate and would face a White House veto even if it succeeded.
The 27 Democratic votes on Wednesday for the bill fell short of the 39 who broke ranks with the White House last November and voted with Republicans in favor of a failed bill that would have allowed health insurers to continue to sell plans canceled under Obamacare.
Supporters of the new bill cast the legislation as an issue of fairness.
They argued that individual consumers should be granted a delay on the penalty because the Obama administration had postponed the implementation of some Obamacare provisions that apply to businesses.
"This is an opportunity to stop the political games and put working Americans first," said House Majority Leader Eric Cantor, a Virginia Republican.
House Minority Leader Nancy Pelosi, a California Democrat, said after 50 such votes, "It's time for Republicans to end their obsession with upending health reform and work with Democrats to strengthen it."
Analysts say a delay on the penalty would undermine the law's aim of extending health coverage to millions of uninsured Americans by destabilizing new private insurance marketplaces established on the expectation the penalty would encourage people to enroll in coverage.
More than 4 million people have already enrolled in private insurance through the marketplaces. The open enrollment period ends on March 31.
One of Obamacare's most unpopular provisions, the individual mandate requires most Americans to be enrolled in health coverage by March 31 or pay a tax penalty that is being phased in over three years. (Reporting by David Morgan and Thomas Ferraro; Editing by Peter Cooney and Andrew Hay)