DUESSELDORF, Germany (Reuters) - German postal workers began staging warning strikes early on Monday to raise pressure on Deutsche Post in a dispute over pay, trade union Verdi said.

The strikes, held in cities including Berlin, Hamburg, Stuttgart, Hanover and Dresden, meant some 3 million letters would go undelivered for the time being, Verdi said.

Warning strikes in Germany usually involve temporary stoppages. However, Verdi also called on postal workers at the weekend to vote for full-blown strike action from May 2 after the failure of wage talks with Deutsche Post.

The talks broke down after the employers made a new offer that fell short of the union’s demand for a 7 percent pay increase. The two sides were also negotiating working hours and job protection.

Dubbed a “mega wage year” by Germany’s biggest industrial union, 2008 has already delivered the biggest pay increases in 16 years for the public sector and steel workers.

In the last two years, Germany has enjoyed its strongest burst of economic activity since reunification in 1990 and workers want a greater share of the success after years of wage moderation that helped boost firms’ profitability.