Oil analysts have raised their average price forecasts for 2016 for the first time in 10 months, but cautioned that investor sentiment may sour short-term without solid improvement in market fundamentals, a Reuters poll showed.

The oil price has risen by about 45 percent from 12-year lows close to $27 a barrel reached in January.

"The recent rally is more a comeback from very bearish sentiment that took place at the beginning of the year with China headlines, Iran sanctions lifted, reasons that we actually found to be an irrational move of the market," Raymond James analyst Luana Siegfried said.

"Regardless, this could signify the start of a recovery as we are approaching the summer, when demand typically picks up in the western hemisphere on the back of higher motor fuel consumption."

Analysts said that without Iran's participation, any deal struck on managing supply at the April 17 meeting in Doha among OPEC and non-OPEC exporters would be little more than symbolic and unlikely to erode a global overhang of unwanted crude.

"Iran's refusal to participate means more countries will need to make greater cuts for longer if such a deal is to be effective. Given diverging interests and persistent distrust, this is unlikely," said Sebastien Marlier, commodities analyst at the Economist Intelligence Unit.

Analysts see U.S. crude futures averaging $39.70 a barrel in 2016, up 80 cents from the February poll forecast. West Texas Intermediate (WTI) has averaged about $33.50 so far in 2016.

Morgan Stanley had the lowest 2016 forecast for Brent at $33 a barrel, while Raymond James had the highest at $53.

(Additional reporting by Koustav Samanta in Bengaluru; Editing by Amanda Cooper and Dale Hudson)