* China's tightening of bank reserves creates nervousness
* Citigroup, Halliburton up after results
* Greece denies it is seeking debt restructure plan
* Futures off: Dow 66 pts, S&P 7.7 pts, Nasdaq 13.25 pts (Updates comment)
By Chuck Mikolajczak
NEW YORK, April 18 (Reuters) - U.S. stocks were poised for a lower open on Monday after China took another step to stem the growth of its economy and worries persisted Greece may need to restructure its debt.
China raised banks' required reserves for the fourth time this year on Sunday, stepping up efforts to fight high inflation.
The move by China hurt commodities, sending copper prices lower. Miner Freeport-McMoran Copper & Gold Inc fell 0.7 percent to $50.81 in premarket.
"China is the real driver why we are seeing the futures down, and that is backed up by the fact that you are seeing a selloff in a lot of commodities," said Peter Jankovskis, co-chief investment officer at OakBrook Investments LLC in Lisle, Illinois.
"That is what is driving the commodity boom ... how quickly they are growing and feeding that. People have an expectation that will continue, and anything that is out there suggesting it will slow down gets them nervous."
Adding to global concerns, Athens reiterated it has no plans to restructure its government debt, a move its central bank chief said would be catastrophic, but markets speculated that some form of debt rescheduling was likely.
Citigroup Inc's stock advanced 1.4 percent to $4.48 before the open after first-quarter profit fell 32 percent, slightly beating expectations, as the bank lost less money on bad loans but struggled to expand business.
Halliburton Co, the world's No. 2 oilfield services company, advanced 0.8 percent to $47.20 in premarket trading after posting a first-quarter profit that beat analysts' estimates as oil companies increased spending on new projects to meet growing oil demand worldwide.
Eli Lilly & Co shed 1.6 percent to $35.42 after the drugmaker reported better-than-expected first-quarter sales and earnings.
S&P 500 futures fell 7.7 points and were below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures fell 66 points and Nasdaq 100 futures fell 13.25 points.
Healthcare stocks will be in the spotlight after Swiss medical device maker Synthes confirmed it is in merger talks with Johnson & Johnson. Reports said the U.S. company was in talks to buy it for about $20 billion. J&J shares edged up 0.07 percent to $60.60 in premarket trade. (Reporting by Chuck Mikolajczak; Editing by Kenneth Barry)