By Susan Cornwell

WASHINGTON (Reuters) - The chairman of a U.S. Senate
committee on Tuesday delayed a vote on the new arms control
treaty with Russia until at least mid-September, after months
of effort to win backers produced scant Republican support.

Democratic Senator John Kerry had wanted the committee to
vote on the new START treaty before the August recess that
starts at the end of this week. He said he would bow to the
requests of senators for more time to study the document.

President Barack Obama signed the strategic arms agreement
with Russian President Dmitry Medvedev in April and sent it to
the Senate in May. Obama said he would like to see the Senate
ratify it this year.

The treaty will need 67 votes to clear the Senate, meaning
at least eight Republican votes are needed. Only one
Republican, Richard Lugar, has so far publicly supported it,
and in recent weeks, the treaty has drawn more Republican
criticism as partisan rhetoric heats up ahead of Nov. 2
congressional elections.

The agreement would cut the number of nuclear warheads
deployed in the United States and Russia by about 30 percent.

"My interest is not in trying to jam this through," Kerry
told the committee at a business meeting. "I respect every
senator's right to further examine it."

Kerry warned that without the treaty, there was no system
in place to verify the two countries' nuclear arsenals, by far
the world's largest. He said he hopes members can vote on it on
Sept. 15 or 16 shortly after returning from a recess.

LUGAR RESTATES SUPPORT

Lugar told the panel he had been prepared to vote now and
"let the chips fall where they may." The treaty was needed
because such documents provided "some visibility of what is
going on" in Russia's nuclear arsenal, he said.

"At some point we need to think about the United States of
America and our security interests," Lugar said.

Lugar's support meant the treaty would have been approved
by the committee had it held the vote this week. But a panel
vote might have irritated other Republicans, whose Senate
leaders have been calling for more time.

A senior administration official said there was reason to
believe more Republicans ultimately would be won over. Some
Republicans have told the White House privately that "they
expect to be there in the end" and vote for the new START, the
official said, asking not to be named.

But key Senate Republicans have made several demands before
they announce publicly whether they will support the treaty.
They urged the Obama administration to release the record of
negotiations to prove its assertion that there were no secret
deals made with the Russians to limit missile defense systems.

To try to meet this demand, a summary of the negotiating
record affecting missile defense has been made available to
senators, Kerry told reporters.

The Senate's No. 2 Republican, Jon Kyl, has sought White
House commitments to modernize the U.S. nuclear weapons that
remain. The administration pledged $80 billion for this over 10
years but Kyl said a key test would be whether Congress
approves some of the money for the next fiscal year.

Arms control advocates charge some Republicans are
recklessly moving the goal posts -- and seeking more arms
spending for their own states.

"It is irresponsible and unnecessary for a few senators to
hold New START and U.S. national security hostage for billions
more dollars for weapons laboratories," said Daryl Kimball,
executive director of the Arms Control Association.

The White House said it remained optimistic about
ratification. "The treaty deserves the same bipartisan support
that past arms control treaties with Russia have received,"
National Security Council spokesman Mike Hammer said.

Under the treaty, each side agreed to reduce the number of
deployed strategic nuclear warheads to no more than 1,550
within seven years, and reestablish on-site inspections.
(Editing by Bill Trott)