* Workers plan to block coal shipments next week
* Economy Minister says JSW situation complicated
(Adds treasury ministry comments)
By Wojciech Zurawski
KATOWICE, Poland, April 20 (Reuters) - Poland may need to delay the initial public offer of JSW, Europe's largest coking coal miner, in the face of mounting worker protests over wages and privatisation, the economy minister warned on Wednesday.
Earlier, workers said they would escalate their ongoing protests by blocking coal shipments starting next Tuesday.
The unions said production would continue next week, but coal would be stored instead of being sent to clients.
"The situation at the company is difficult and complicated, while the lack of agreement (between workers and management) makes making business decisions difficult," Economy Minister Waldemar Pawlak told journalists.
But Poland's treasury ministry, which oversees the sale of state assets, said it was determined to follow through with its plans to float JSW, which is estimated to be worth as much as $3.6 billion.
It had planned to complete the IPO by the end of June as part of a 15 billion zlotys ($5.5 billion) privatisation drive.
"We should not give in to pressure from union activists who are not interested in making JSW a transparent company listed on the stock exchange," the ministry said in a statement on its web site.
Although the treasury manages privatisation procedures and has prepared a prospectus for JSW, the flotation must be cleared by the economy ministry, which oversees the mining sector.
JSW miners have already held a one-day strike earlier this week to press for large pay increases, 10-year job guarantees and assurances that Poland would always retain at least 51-percent of the company.
JSW estimated related losses at around 30 million zlotys.
"The protest will be continued until management meets with us and fulfils our demands. We also count on the Economy Ministry to act as a mediator between us and management," said Piotr Szereda, a spokesman for the protesting miners.
Poland is aiming to sell up to 49 percent of the miner, which would leave it with 51 percent. Further details of the transaction have not been revealed yet.
Deputy Treasury Minister Krzysztof Walenczak told Reuters last week that opposition to the privatisation of the miner should not hold up the IPO. (Editing by Will Waterman and Mark Potter) ($1=2.753 Zloty)