(Adds quotes from Rostowski interview)
By Pawel Florkiewicz
KRYNICA, Poland, Sept 10 (Reuters) - Poland aims to join the euro in 2011, Prime Minister Donald Tusk said on Wednesday, making his firmest statement yet on when the EU's largest former communist economy could adopt the common currency.
Markets had pushed back expectations for when the Poles could enter the euro bloc till 2013 or later and the zloty and other Central European currencies surged after Tusk's speech, made at the opening of Poland's biggest annual economic forum.
But many analysts remained cautious on assessing the weight of Tusk's commitment, saying they would wait for more detail on how the government plans to overcome remaining political, legal and procedural obstacles.
"For the first time, standing here in front of you, I take advantage of the occasion ... to formulate precisely one of our main goals," Tusk told the forum in the southern mountain resort of Krynica.
"Our goal (to adopt the euro) is 2011. This is our government's goal. This is a difficult but feasible task."
Tusk's economically liberal government had until now refrained from giving a firm target date for joining the 15-nation euro zone.
Slovakia, which like Poland joined the EU in 2004, is set to become the 16th member of the zone next January, but political apathy and high inflation have been seen holding up the arrival of other Central and Eastern Europe's fast-growing economies.
The latest Reuters poll of economists saw Poland joining in 2013 along with the Czech Republic and Latvia, one year after it predicted tiny Estonia would enter.
By close of trade, the zloty <PLN=> <EURPLN=> had gained 1.6 percent against the euro. Hungary's forint <EURHUF=> and the Czech crown <EURCZK=> both rose more than one percent intraday.
Finance Minister Jacek Rostowski has said Poland could potentially take the initial step of putting the zloty in the ERM-2 currency grid next year, followed by euro adoption in 2011 or 2012.
Euro candidate currencies must spend a minimum of two years in ERM-2 before they can adopt the euro, and past experience has shown countries need closer to three to prepare from the moment of joining the currency grid.
In an interview given on Wednesday before Tusk's remarks, Rostowski told Reuters Poland was making good progress towards meeting the criteria for eventual euro membership.
He also said it is better for a country to be in an easing monetary mode and to have interest rates close to those of the European Central Bank for ERM-2 entry. Poland's main interest rate is now at 6 percent against 4.25 percent in the eurozone.
CREDIBILITY
Asked whether Poland would need to enter ERM-2 next year, Tusk told reporters: "The calendar is precisely set by the procedures. The budget will add to our credibility as far as the perspective for adopting the euro goes."
On Tuesday, the government approved a 2009 draft budget that slashes the deficit by almost half. To adopt the euro, a country must run a budget deficit of no more than three percent of GDP.
Tusk's comments come amid a legal debate on whether his coalition government will need to find additional votes in parliament to change the constitution before adopting the euro. The constitution says it is the sole right of the Polish central bank to set monetary policy and issue money.
Tusk said he would need public support for joining the euro.
"I believe that in the future we will gain such acceptance. I am not saying a referendum but this has to be for the people, not only the government," he said.
Rostowski told Reuters a referendum on euro entry was an option for Poland.
Central bank Monetary Policy Council members Dariusz Filar and Marian Noga said after Tusk's statement that entry in 2011 was technically possible, although Filar cautioned it could be the second half rather than the beginning of the year.
"This is a very important statement (by Tusk) which has strengthened the zloty but I would be cautious," said Bank BPH economist Adam Antoniak. "Theoretically euro adoption is possible in 2011, but technically the probability is small."
Other analysts also struck a cautious note.
"Given the economic uncertainties and distress, we find it highly unlikely that the European Central Bank and the European Commission would accept a swift Polish euro adoption," said Lars Rasmussen of Danske Bank in a note.
"We think that euro adoption in 2012-2013 is more likely." (Additional reporting by Kuba Jaworowski and Adrian Krajewski; Writing by Patrick Graham and Gareth Jones; Editing by Ruth Pitchford)