* Weekly jobless claims rise unexpectedly
* Avago rises after agreeing to buy Broadcom for $37 bln
* Abercrombie & Fitch rises after positive forecast
* Futures down: Dow 60 pts, S&P 4.5 pts, Nasdaq 6 pts (Adds details, comment, updates prices)
By Tanya Agrawal
May 28 (Reuters) - Wall Street was set to open lower on Thursday on concerns about a Greek default and an unexpected rise in weekly jobless claims.
European officials downplayed talk that Greece and its lenders were drafting an agreement that would provide Athens much-needed debt relief.
Initial claims for state unemployment benefits rose by 7,000 to a seasonally adjusted 282,000 for the week ended May 23, the Labor Department said on Thursday. Economists on average had expected claims falling to 270,000.
World markets were also under pressure after investors in China said several major brokerages had tightened requirements on margin financing, triggering fears of further steps to reduce leverage in the red-hot market.
Wednesday was the strongest day for the S&P 500 since May 14 and the Nasdaq Composite's strongest since late January, lifting it to its first record close since April 24.
However, low volumes and muted trading activity at the start of summer suggested the gains were not sustainable.
"There is a loss of liquidity in the market," said Jack Ablin, chief investment officer at BMO Private Bank in Chicago.
"Investors should party as long as the music is playing because once it stops you're going to have to deal with the headache."
S&P 500 e-mini futures were down 4.50 points and their fair value - a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract - indicated a lower open.
Dow Jones industrial average e-mini futures were down 60 points and Nasdaq 100 e-mini futures were off 6 points.
Avago shares rose 4.2 percent to $147.40 in premarket trading after it agreed to buy fellow chipmaker Broadcom for $37 billion. Broadcom fell 0.4 percent to $56.90. Both stocks had risen strongly on Wednesday on reports of an imminent deal.
Abercrombie & Fitch rose 3.8 percent to $20.40 after the teen apparel retailer said it expects comparable sales to improve in the second half of the year.
GoPro jumped 5.7 percent to $56.37 on reports that the action camera maker will launch a new spherical camera mount and a drone.
Sanderson Farms fell 3.5 percent to $81.54 after the third-largest U.S. poultry producer reported lower-than-expected quarterly net sales and profit. (Additional reporting by Sweta Singh in Bengaluru; Editing by Savio D'Souza)