* Investors watching situations in Greece, Ukraine
* S&P 500 coming off record closing high
* Celsus shares plummet after drug fails study
* Dow, S&P 500 and Nasdaq all fall 0.3 pct (Updates to the open of U.S. trading)
By Ryan Vlastelica
NEW YORK, Feb 17 (Reuters) - U.S. stocks edged lower on Tuesday, with the S&P 500 pulling back from record levels as investors continued to grapple with the uncertainty over a Greek debt deal and a fragile Ukraine truce.
Equities have been in an uptrend lately, with major indexes notching a second week of solid gains last week. Much of the advance came on signs of progress for the debt deal in Greece, as well as reduced tension between Russia and Ukraine.
Both situations appeared less stable over the long weekend when U.S. stock markets were closed Monday for Presidents Day. European Union finance ministers pressured Greece to remain in an international financial rescue program after talks collapsed on Monday. U.S.-listed shares of the National Bank of Greece fell 12 percent to $1.41.
"This has been a well-advertised point of confusion, so it isn't taking the market by surprise," said Liam Dalton, president of Axiom Capital Management in New York.
"While there is concern, and it has become in vogue to say that stocks are expensive, it is hard to say what they're expensive relative to. Cash remains abundant and interest rates are low, and we should generally go up in an environment like that."
In eastern Ukraine, Pro-Russian separatists said they would not carry out an agreement to pull back heavy guns, putting a shaky peace deal at risk.
While the United States has little direct exposure to Greece, Ukraine or Russia, any breakdown in either place could lead to continued volatility in Europe, a major trading partner.
The day's losses were slight but broad, with nine of the 10 primary S&P 500 sectors lower on the day. Energy was the biggest decliner, falling 0.8 percent alongside a drop in crude oil, which sank 2.5 percent after earlier rising as much as 1.7 percent.
"We think oil is likely to have stabilized, but we don't see meaningful upside in the next six months," said Dalton, who oversees about $2.2 billion in assets.
Transocean Ltd fell 2.9 percent to $18.49 a day after the company slashed its dividend and said its chief executive stepped down.
Medtronic Plc added 2.4 percent to $77.06 after reporting better-than-expected earnings growth, boosted by higher sales of its cardiac devices.
On the downside, Celsus Therapeutics plummeted 81 percent to $1.14 after the company's lead drug failed a mid-stage study. VBL Therapeutics Inc dropped 55 percent to $6.38 after it said it would stop developing its experimental inflammatory drug to fight ulcerative colitis and psoriasis.
The Dow Jones industrial average fell 57.23 points, or 0.32 percent, to 17,962.12, the S&P 500 lost 6.87 points, or 0.33 percent, to 2,090.12 and the Nasdaq Composite dropped 12.23 points, or 0.25 percent, to 4,881.61.
NYSE decliners outnumbered advancers 1,702 to 1,090, for a 1.56-to-1 ratio; on the Nasdaq, 1,303 issues fell and 1,085 advanced, a 1.20-to-1 ratio.
The S&P 500 was posting 21 new 52-week highs and 2 lows; the Nasdaq Composite was recording 53 new highs and 13 lows. (Editing by Nick Zieminski)