* If not, a rating cut is on the cards - Moody's analyst
* Rating agency wants concrete evidence of implementation
(Adds more comments, bond yield spreads, context)
LONDON, March 4 (Reuters) - Greece must implement its austerity plan perfectly or face the prospect of a rating cut, Moody's senior analyst Sarah Carlsson told Reuters Insider TV on Thursday.
"Anything short of a perfect implementation would result in some form of rating action," Carlsson said. "The magnitude of that action (would be) proportionate to the kind of shortfall we're seeing."
Carlsson said Moody's has Greece rated A2 with a negative outlook.
Click on link.reuters.com/zev23j to watch the interview.
"One way we judge (the rating is appropriate) is whether Greece can achieve a deficit reduction to 8.7 percent of gross domestic product in 2010," she added.
"We want to see concrete evidence of implementation... The austerity plan provides certainty for 2010. But what is going to happen in 2011 and beyond is what we want to know."
Carlsson said that "the strike action we have seen this morning (in Greece) is just a sign of how ambitious the government's plans are."
Greece needs to refinance about 20 billion euros of debt maturing in April and May, and officials previously said its funding needs were met until mid-March.
Greece opened a much-anticipated new 10-year syndicated bond sale earlier on Thursday.
The order book was reported to have closed at 16 billion euros at 1100 GMT, with a final pricing of midswaps plus 300 basis points, according to a bank source.
The 10-year Greek government bond yield spread over euro zone benchmark German Bunds GR10YT=RREU10YT=RR was at 289 basis points, compared with 287 bps at the European settlement close on Wednesday.
Reporting by George Matlock; editing by John Stonestreet