* Investors watching situations in Greece, Ukraine
* S&P 500 ends above 2,100
* Celsus shares plummet after drug fails study
* Indexes: Dow up 0.2 pct; S&P 500 up 0.2 pct; Nasdaq up 0.1 pct (Updates to close)
By Caroline Valetkevitch
NEW YORK, Feb 17 (Reuters) - The S&P 500 ended above 2,100 at another record high on Tuesday as optimism grew that a debt deal would be reached with Greece and as bond prices sold off.
In a possible sign of progress for Greece, a source told Reuters the country intends to ask for an extension of a loan agreement Wednesday. The report follows a collapse of deal negotiations on Monday, which led to European Union finance ministers pressuring the country to remain in an international financial rescue program.
Late in the session, though, broadcaster ZDF reported the German finance minister said an extension was not up for debate.
U.S. Treasury debt prices sold off, pushing benchmark 10-year note yields to seven-week peaks, on expectations the Federal Reserve could bump up rates as early as June. Minutes from the last Fed meeting are due Wednesday.
"We've seen more of a risk-on trade," said Bucky Hellwig, senior vice president at BB&T Wealth Management in Birmingham, Alabama. "Because bonds are so low globally, it creates an interest in equities that perhaps the risk is worth taking to get the higher return."
Among the S&P 500's biggest positives, shares of Medical device maker Medtronic Plc, which last month completed the $49.9 billion purchase of Ireland-based Covidien Plc, rose 3.7 percent at $78.07. Medtronic reported a better-than-expected third-quarter profit, driven by solid growth in its cardiac and vascular business.
The Dow Jones industrial average rose 28.23 points, or 0.16 percent, to 18,047.58, the S&P 500 gained 3.35 points, or 0.16 percent, to 2,100.34, a record high. The Nasdaq Composite added 5.43 points, or 0.11 percent, to 4,899.27.
U.S.-listed shares of the National Bank of Greece ended up 1.2 percent at $1.63 after falling more than 13 percent earlier in the session.
Shares of Transocean Ltd recovered to close flat $19.05 a day after the company slashed its dividend and said its chief executive stepped down.
Among decliners, Celsus Therapeutics plummeted 81.4 percent to $1.15 after the company's lead drug failed a mid-stage study. VBL Therapeutics Inc dropped 65.5 percent to $4.87 after it said it would stop developing its experimental inflammatory drug to fight ulcerative colitis and psoriasis.
A fragile Ukraine truce added uncertainty to the market. In eastern Ukraine, Pro-Russian rebels fought their way into an encircled government bastion and were battling street-to-street, all but dashing hopes that a European-brokered peace deal would end months of conflict.
About 6.2 billion shares changed hands on U.S. exchanges, below the 6.7 billion average for the last five sessions, according to BATS Global Markets.
NYSE decliners outnumbered advancers 1,776 to 1,337, for a 1.33-to-1 ratio; on the Nasdaq, 1,533 issues rose and 1,199 fell, a 1.28-to-1 ratio favoring advancers.
The S&P 500 posted 64 new 52-week highs and 2 new lows; the Nasdaq Composite recorded 115 new highs and 22 new lows. (Editing by Nick Zieminski)