(Adds Verdi chief in paragraph 4)
BERLIN, April 11 (Reuters) - Trade unions in Germany piled more pressure on public sector employers with a second day of nationwide wage strikes on Wednesday, as more than 25,000 workers staged walkouts at hospitals, childcare centers and waste depots.
No flights were affected by Wednesday's action.
On Tuesday, walkouts caused widespread disruption to air travel, including the cancellation of hundreds of flights, leaving thousands of passengers stranded.
The Verdi union wants a 6 percent pay rise for 2.3 million public sector employees, but the federal government and municipalities have rejected the demand as too high. The next round of negotiations is due on April 15.
Verdi chief Frank Bsirske told Reuters on Wednesday that employers would have to offer something concrete at the third round of talks to avoid escalation. "Anything else would be a confrontation," he said.
The southern states of Bavaria and Baden-Wuerttemberg were among the worst hit on Wednesday but walkouts and demonstrations also affected other regions, including North Rhine-Westphalia, Germany's most populous state.
The president of the Bavarian civil servants' union, Rolf Habermann, told Reuters employers should make an offer reflecting the strength of Germany's economic upswing.
"There have been enough words exchanged, the rituals have been maxed out," Habermann said.
Germany, Europe's biggest economy, is in solid shape, with buoyant tax revenues and a record budget surplus. Falling unemployment, inflation-busting pay rises and low borrowing costs are fueling a consumer-led upswing.
The European Central Bank is keeping a close eye on the German wage negotiations for any sign that wage growth is picking up, potentially lifting inflation and giving the ECB added leeway to start winding down its massive stimulus program. (Reporting by Thorsten Severin Writing by Charley-Kai John Editing by Raissa Kasolowsky and John Stonestreet)