UPDATE 1-S&P surprisingly changes outlook on Poland's rating to positive

* S&P raises outlook on BBB+ rating to positive

* Cites Poland's solid economic and fiscal performance

* Nearly all analysts expected no change in rating or outlook

* Positive outlook signals rating may be raised in 24 months (Adds finance ministry comment, details)

WARSAW, April 13 (Reuters) - Rating agency S&P Global surprisingly changed the outlook on Poland's BBB+ sovereign rating to positive from stable on Friday citing the country's robust economic and fiscal performance.

S&P, which currently has the lowest rating on Poland from the three major rating agencies, said the positive outlook indicated an increased likelihood that it would upgrade Poland within the next 24 months.

"Our decision to revise the outlook to positive from stable reflects our view that Poland's economic expansion will last longer than we had previously thought, benefiting fiscal performance more than we had previously projected," S&P said.

Twelve out of fourteen analysts polled by Reuters earlier this week expected the rating and the outlook to remain unchanged. Just one expected the outlook to be improved.

"The outlook revision also speaks to our rising confidence that tax administration reforms have generated a secular increase in public revenues of around 0.5 percent of GDP," the agency said.

S&P also said it could raise Poland's rating if the economy continued to expand at a buoyant pace without generating large net external financing needs, and should government debt to GDP remain on a clear downward trend.

Poland's Finance Minister Teresa Czerwinska welcomed the outlook change.

"We are waiting for the next natural step from the agency that will consist of raising the rating itself," she said in a statement, calling S&P "the most critical" agency towards Poland.

Poland's economic growth accelerated to 4.6 percent last year and the fiscal deficit fell to its lowest level in more than two decades, with public debt falling by 4 percentage points.

"Finally, we believe that the government will be able to navigate risks associated with economic overheating as well as complex relations with the EU, the source of direct economic transfers to Poland," S&P said.

The European Union's executive on Wednesday said it hoped for a deal "very soon" in a fundamental dispute with Poland over judicial independence and sources said mid-May could be a key date.

S&P downgraded Poland's rating to BBB+ in early 2016 saying at that time the government of the currently ruling right-wing Law and Justice party (PiS) had weakened the independence of key institutions, including the judiciary.

Fitch rates Poland at A-, one notch higher than S&P. Its peer Moody's has the rating two notches higher at A2, both with a stable outlook. (Reporting by Marcin Goettig)