* PKN agrees with unions to keep wages flat this year
* KGHM management plans to freeze wages in 2009
* KGHM labour unions oppose move
(Adds analyst, closing prices)
By Agnieszka Barteczko and Patryk Wasilewski
WARSAW, March 10 (Reuters) - Poland's state-controlled industrial heavyweights, refiner PKN Orlen <PKNA.WA> and copper miner KGHM <KGHM.WA>, moved on Tuesday to freeze wages this year due to the economic slowdown and falling commodity prices.
PKN said its unions agreed to keep wages flat this year, and bonuses would be reduced by nearly a fifth after the group reported its first ever annual loss last week. The group employs 23,000 in Poland, Lithuania and the Czech Republic, but the agreement applies only to its main refinery.
KGHM, which has 18,500 workers concentrated in southwest Poland, wants to freeze salaries and also cut bonuses in exchange for cutting only 334 jobs, even as it struggles with low copper prices and one of the industry's highest cost bases.
Polish wages have been climbing since Poland joined the European Union in 2004, recording a double-digit rise last year, thanks to a booming economy.
At PKN, the average salary rose by 9.5 percent in 2008.
But as the boom years came to an abrupt end, many Polish companies have reduced their headcounts to cut costs.
"The managements at both companies are taking the right step, considering the crisis we are experiencing," said Pawel Puchalski, analyst at BZ WBK.
KGHM's powerful unions warned they opposed the unilateral move and could start a collective dispute as a step that could lead to the miner's first strike in nearly two decades.
"A wage freeze is de facto a wage cut," Ryszard Zbrzyzny, leader of KGHM's No. 2 union, told Reuters. "We could enter into a collective dispute, but we need to coordinate this with other large unions at KGHM."
His comments were echoed by Jozef Czyczerski, who heads KGHM's top union.
"The market is giving KGHM's executives strong arguments," said Puchalski. "Up to this point, the unions have had a strong position and are taking advantage of it."
KGHM shares, buoyed by a rise in copper prices, closed 5 percent higher, while PKN was nearly flat. Warsaw's benchmark WIG20 index <
> rose 1.8 percent. (Additional reporting by Adrian Krajewski; Writing by Chris Borowski; Editing by Will Waterman and Sharon Lindores)