Germany's Social Democratic Party (SPD) has agreed a series of economic demands ahead of coalition talks with Chancellor Angela Merkel next week.
SPD leaders promised the 200 members meeting on Sunday that they would win concessions, including a minimum wage, from Mrs Merkel's centre-right bloc.
Mrs Merkel's alliance won recent elections but fell short of a majority.
In 2005-2009 the SPD formed a "grand" coalition with Mrs Merkel's Christian Democrats (CDU) and the allied CSU.
But correspondents say the experience has made them wary about working with the CDU/CSU again.
A majority of the 200 members meeting on Sunday backed a statement agreeing to the start of formal talks.
An internal SPD document seen by Reuters before the meeting said the party would insist that 10 demands were non-negotiable.
They include a minimum wage of 8.50 euros (£7) per hour, equal pay for men and women, greater investment in infrastructure and education, and a common strategy to boost eurozone growth and employment.
The party would also demand equal pensions for the elderly in the former West and East Germany and measures to make it easier to combine work with family life, Reuters reported.
No mention was made of tax increases for the wealthiest, which the SPD had campaigned on during September's election.
Allies of Chancellor Merkel have said they could live with a minimum wage but not with the higher taxes.
The SPD also wants to move away from tough austerity measures and focus more on growth and job creation.
It is understood that talks on coalition policies and cabinet posts could begin as early as next Wednesday and could last more than a month.
The BBC's Stephen Evans in Berlin says a grand coalition is likely, and with it a slight move of the German government to the left, with more government spending and a more generous attitude towards eurozone countries in trouble.
But it would not be a major shift - Chancellor Merkel would remain very much in charge, our correspondent says.
He adds that it will be interesting to see if the SPD pushes for the post of finance minister in any new government, as the post is currently filled by the CDU's Wolfgang Schaeuble, seen as the driver of Germany's tough economic policy.
Mrs Merkel's previous coalition allies, the Free Democrats, failed to win any seats in September, leaving her seeking a new partner.
Her options narrowed last week when the Greens announced that talks with the CDU/CSU had failed.
At the polls on 22 September, the CDU/CSU took about 41.5% of the vote, the SPD 26%, the former communist Left Party 8.6% and the Greens 8.4%.