By David Morgan

WASHINGTON (Reuters) - Senate Republican leader Mitch McConnell is urging the National Football League and other professional sports leagues not to support President Barack Obama's healthcare reform law, calling Obamacare divisive and unpopular.

In a June 27 letter to NFL Commissioner Roger Goodell, McConnell and fellow Republican Senator John Cornyn accused the Obama administration of drawing the league into "one of the most divisive and polarizing issues of our day" by trying to enlist its help in promoting subsidized health coverage for millions of uninsured Americans.

"Given the divisiveness and persistent unpopularity of the health care law, it is difficult to understand why an organization like yours would risk damaging its inclusive and apolitical brand by lending its name to its promotion," McConnell and Cornyn told the NFL.

The two lawmakers also sent similar letters to Major League Baseball, the National Basketball Association, the National Hockey League, the Professional Golfers' Association and the National Association for Stock Car Auto Racing, or NASCAR.

U.S. Health and Human Services Secretary Kathleen Sebelius told reporters on Monday that the administration was in discussions with the NFL and other sports groups.

"The NFL, for instance, in the conversations I've had, has been very actively and enthusiastically engaged because they see health promotion as one of the things that is good for them and good for the country," she said.

But the league's response to McConnell seemed less than enthusiastic.

"We have responded to the letters we received from members of Congress to inform them we currently have no plans to engage in this area and have had no substantive contact with the administration about (the law's) implementation," said NFL spokesman Greg Aiello.

The Department of Health and Human Services declined to comment.

The White House and HHS are reaching out to professional sports leagues, teams and players in hopes of encouraging young men and women to sign up for health coverage through new online markets that are slated to begin open enrollment on October 1.

McConnell's letters represent a new line of Republican attack on Obama's Patient Protection and Affordable Care Act, known as Obamacare. Republicans in the House of Representatives have voted 37 times to repeal or defund the law, which they see as a costly and unnecessary expansion of government.

The party is now taking aim at administration efforts to rally private sector support, including fundraising by Sebelius on behalf of the non-profit group Enroll America, which is helping to lead a private-sector grassroots campaign aimed at driving enrollment.

Democrats and other reform advocates say Republicans are trying to undermine the law's implementation ahead of the 2014 congressional elections, in which the party hopes to win control of the Senate.

Analysts say the ability of the online marketplaces, or exchanges, to attract younger beneficiaries will help determine whether Obama's signature domestic policy achievement becomes a success or a failure.

(Reporting by David Morgan; Editing by Eric Beech)

[Image: Senate Minority Leader Mitch McConnell (R-KY) speaks to the media on Capitol Hill in Washington on June 18, 2013. By Yuri Gripas for Reuters.]