TREASURIES-Yields drop slightly as poll shows Brexit vote gaining

* Yields fall after UK poll shows Brexit vote gains

* Yellen to testify before Washington lawmakers

* Treasury to sell $34 billion five-year notes

By Karen Brettell

NEW YORK, June 21 (Reuters) - U.S (Other OTC: UBGXF - news) . Treasury yields fell

slightly on Tuesday after a new opinion poll showed that the

campaign for Britain to stay in the European Union has lost some

of its lead over the rival "Out" camp ahead of Thursday's EU

membership referendum.

The Survation poll, which was conducted for spread-betting

firm IG (LSE: IGG.L - news) , put support for "In" at 45 percent, ahead of "Out" at

44 percent, IG said. Its previous poll, published late on

Saturday, had shown "In" ahead of "Out" by 45 percent to 42

percent.

Treasury moves have been dominated in the past few sessions

by fluctuating expectations on whether Britain is likely to vote

to remain in, or leave, the European Union.

"All eyes are on that vote," said Ian Lyngen, a senior

government bond strategist at CRT Capital in Stamford,

Connecticut.

Yields rose to one-and-a-half week highs on Monday after two

opinion polls suggested that the "Remain" camp had recovered

some ground in Britain's EU referendum debate following the

murder of a pro-EU lawmaker.

Benchmark 10-year notes were last yielding 1.68

percent, down from 1.69 percent earlier on Tuesday. The bonds

closed on Monday with yields of 1.67 percent.

Concerns about the potential ramifications of a British exit

from the EU are likely to dominate market moves this week, even

as Federal Reserve Chair Janet Yellen is due to testify before

lawmakers in Washington on Tuesday and Wednesday.

"Yellen's comments are going to be of interest, but I don't

know if they are going to be able to really move the market in

the context of what we're expecting later this week from the UK

referendum," Lyngen said.

The Fed last week cut its economic growth outlook and

signaled it still planned to raise rates twice in 2016, though

six of its 17 policymakers were projecting just one increase

this year. Only one Fed policymaker had done so when economic

forecasts were last issued in March.

The Treasury will also sell $34 billion in five-year notes

on Tuesday, the second sale of $88 billion in coupon-bearing

short-and-intermediate-dated supply this week.

The government sold $26 billion of two-year notes to

moderate demand as direct bidders purchased the fewest two-year

issue since January 2015.

The Treasury will also sell $28 billion in seven-year notes

on Wednesday.

(Editing by Will Dunham)