* 64 senators urge comprehensive approach to deficit
* 23 Republicans say may not support debt limit increase
* Obama signs stopgap spending bill to prevent shutdown
By Andy Sullivan
WASHINGTON, March 18 (Reuters) - With the U.S. Congress fighting over short-term spending levels, Senate lawmakers are urging President Barack Obama to lead broader efforts to get stubborn budget deficits under control over the long term.
In a letter to Obama on Friday, a bipartisan group of 64 senators said he should help craft a deficit-reduction package that included spending cuts, tax reform and changes to entitlement programs like Medicare and Social Security.
The letter, signed by 32 Democrats and 32 Republicans, was released as Obama signed a bill that bought lawmakers more time to resolve a stalemate over spending levels for the current fiscal year and averts a government shutdown.
“By approaching these negotiations comprehensively, with a strong signal of support from you, we believe that we can achieve consensus on these important fiscal issues,” the lawmakers said in the letter.
Separately, a group of 23 Republican senators warned Obama they might not vote to increase the United States’ debt limit without a commitment from him to tackle the cost of entitlements, which are projected to double over a decade.
Failure to raise the debt ceiling could force the nation to default on its debt obligations, a move that would roil bond markets, damage the U.S. credit rating and possibly endanger its economic recovery.
Lawmakers from both parties have criticized Obama for not getting more involved in a budget debate that has consumed Congress this year.
White House aides are currently working with Republicans to end a standoff that has forced the entire U.S. government to operate on a temporary basis for the past six months, which has hampered everything from airport safety to military readiness.
Obama signed a sixth stopgap bill on Friday that will fund the government through April 8, as lawmakers try to reconcile rival spending plans that are about $50 billion apart for the current fiscal year, which ends Sept. 30.
Lawmakers, however, already are eyeing next year’s budget, which Republicans say will tackle entitlements and annual spending, and are considering a simplification of the tax code that would lower rates and eliminate loopholes.
And, likely by the end of May, Congress will need to approve an increase in the government’s $14.3 trillion debt ceiling. Republicans see that vote as an opportunity to force action from the White House.
“Without action to begin addressing the deficit, it will be difficult, if not impossible, for us to support a further increase in the debt ceiling,” wrote the group of 23 Republicans, which includes moderates and conservatives and party leaders like Senator Lamar Alexander.
A commission set up by Obama last year recommended simplifying the tax code, imposing spending caps, raising the retirement age, cutting agriculture subsidies and reforming healthcare payments.
Though the plan failed to win enough support to force a vote in Congress, six senators are preparing legislation based on its recommendations.
Republican Senator Mike Johanns, who signed both letters to Obama, said lawmakers needed the president’s leadership to help make politically difficult decisions necessary to bring down budget deficits that have hovered around 10 percent of GDP in recent years.
“I do not believe that the hard things that need to be done can be done without the White House being involved every step of the way,” Johanns said on a conference call.
Editing by Paul Simao