SINGAPORE - Investors should buy Asian stocks outside Japan after valuations dropped and before sentiment strengthens further, Goldman Sachs Group Inc said.

"By the time all the lights turn green, the race will already be well under way," Goldman Sachs analysts led by Timothy Moe wrote in a note on Thursday. "Sentiment and valuation will improve as the year progresses, and we would prefer to be early."

The MSCI Asia-Pacific excluding Japan Index remains 0.5 percent lower this year, having rebounded from year-to-date losses of as much as 9.7 percent. Stocks slid earlier this year on concern that China will tighten lending to combat faster inflation and that Greece's debt crisis will spread.