* Existing home sales data on tap

* Goldman cuts Boeing to sell rating

* Valeant, Salix agree to merger deal

* Futures: Dow off 39 pts, S&P off 4 pts, Nasdaq up 0.5 pt (Adds quote, updates prices)

By Chuck Mikolajczak

NEW YORK, Feb 23 (Reuters) – U.S. stocks were poised to open modestly lower on Monday, after the Dow and S&P closed at records on the heels of an agreement by euro zone finance ministers to extend Greece’s bailout by four months provided it draws up a list of reforms.

Greece will present its economic reform plans on Monday to seal the euro zone financial lifeline, but the government drew criticism from a veteran leftist and ruling party member that the deal let voters down. The deal is conditional on Greece’s European and IMF creditors accepting the reform list.

“In spite of Germany taking a hard line, the proposals will most likely be accepted by the EU and the reason for that is simply Greece cannot afford to depart from the euro zone, not because Greece is a big economy, but from a psychological standpoint,” said Peter Cardillo, chief market economist at Rockwell Global Capital in New York.

“The EU does not want Greece to leave, because if (it does), it sets a precedent and opens up a new can of worms – who would be next?”

The equity market gains led each of the three major Wall Street indexes to their third weekly advance on Friday, with the Nasdaq on an eight-session winning streak as it closed in on the 5,000 mark for the first time in nearly fifteen years.

Existing home sales data is due at 10:00 a.m. (1500 GMT), the first in a flurry of economic reports this week that will help investors gauge the strength of the housing sector.

S&P 500 e-mini futures were down 4 points and fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract, indicated a slightly lower open. Dow Jones industrial average e-mini futures fell 39 points and Nasdaq 100 e-mini futures added 0.5 point.

Oil prices fell, with Brent down 2.4 percent to $ 58.76 and WTI crude off 3.6 percent at $ 48.99 a barrel on oversupply concerns and a stronger dollar.

Canada’s Valeant Pharmaceuticals International Inc agreed to acquire gastrointestinal drugmaker Salix Pharmaceuticals Ltd in an all-cash deal valued at about $ 10.1 billion, the companies said on Sunday. U.S. listed shares of Valeant gained 8.7 percent to $ 188.30 while Salix slipped 0.9 percent to $ 156.45 in premarket trading.

Asahi Kasei Corp, a Japanese chemicals maker, said it would buy Polypore International Inc’s energy storage segment for $ 2.2 billion, betting on the growth of hybrid and electric cars. Polypore shares jumped 12 percent to $ 59.30 before the opening bell.

Home Loan Servicing climbed 7.9 percent to $ 18.08 in premarket after the company agreed to be acquired by New Residential Investment Corp for about $ 1.3 billion. [ID:L4N0VX2KR}

Dow component Boeing fell 1.8 percent to $ 155.49 after Goldman Sachs cut its rating on the aircraft maker to “sell” from “neutral.”

(Editing by Bernadette Baum)