By Andrew Quinn

WASHINGTON (Reuters) - Secretary of State Hillary
Clinton pleaded with U.S. senators Wednesday to back a new
arms control treaty with Russia, saying a delay in ratification
could hurt U.S. security and create dangerous uncertainty over
broader nuclear control efforts.

Clinton said she was confident that reluctant Republicans
would eventually swing behind the new START treaty when they
vote in mid-September, saying the nuclear pact was too
important to fall victim to U.S. election-year politics.

"Once the new START treaty is ratified and enters into
force, it will advance our national security and provide
stability and predictability between the world's two leading
nuclear powers," Clinton said in a statement.

The new START treaty -- one of the central planks of the
Obama administration's nuclear policy -- has run into choppy
waters in the Senate, where only one Republican has come out in
favor of ratification.

The treaty, which President Barack Obama signed with
Russian President Dmitry Medvedev in April, requires 67 votes
to clear the Senate, meaning at least eight Republican votes
will be needed for it to become law. Clinton is counting on
Democratic support.

This month the Senate Foreign Relations Committee delayed a
vote on ratification until the middle of September to give
senators more time to study the document.

The treaty would cut the number of nuclear warheads
deployed by the United States and Russia by about 30 percent.
Clinton said this would not limit U.S. efforts to modernize its
own nuclear force and maintain a secure nuclear deterrent for
U.S. allies, friends and partners.

Ratification will also allow the United States to resume
on-site inspections of Russia's nuclear arsenal which have been
suspended for more than eight months following the lapse of the
earlier START agreement between the two sides.

"This is a critical point. Opposing ratification means
opposing the inspections that provide us a vital window into
Russia's arsenal," Clinton said.

"As time passes, uncertainty will increase. With
uncertainty comes unpredictability, which when you're dealing
with nuclear weapons is absolutely a problem that must be
addressed."

Russia on Saturday accused the United States of breaching
its obligations on weapons proliferation, a sign of strained
ties between the two former Cold War foes despite their efforts
to "reset" relations.

BIPARTISAN APPEAL

Clinton stressed the bipartisan legacy of U.S. arms control
efforts stretching back to Republican President Ronald Reagan,
and underscored Obama administration plans to spend more than
$80 billion over the next decade to modernize and improve the
U.S. nuclear capabilities.

Her words were clearly aimed at Republicans in the Senate,
among whom only Senator Richard Lugar of Indiana has publicly
said he will support the treaty.

Republican criticism has increased as partisan rhetoric
heats up ahead of the Nov. 2 congressional elections, where
Obama's fellow Democrats are braced for potentially big losses
among voters frustrated by the halting pace of the U.S.
economic recovery.

Senator Jon Kyl, the number two Republican in the Senate,
said he would seek at up to $10 billion more to modernize the
U.S. nuclear force -- a demand which could be difficult to meet
by the end of the year.

Clinton said that despite this, the administration had
indications that the treaty would ultimately win "much more
bipartisan support" as senators ponder the alternatives.

"I believe that this treaty is too important and it will
merit the most thoughtful and substantive response from members
of the Senate. It should not be in any way caught up in
election year politics," she said.

(Editing by Jackie Frank)