"We're taking Poland's concerns very seriously," said Gabriel, who is also Germany's economy minister, after meeting his Polish counterpart Mateusz Morawiecki in Warsaw.
"We've told the Russian side that we won't carry out the project without guarantees ... that gas supplies are secured to eastern Europe," he said.
Poland has claimed the Nordstream 2 pipeline undermines the European Union's strategic interests and violates competition rules, adding that revenue from the project could end up in Russian state coffers and be spent on
"We're a little worried about Polish security, not just in terms of geopolitics but also gas," Morawiecki told reporters on Friday.
No timeframe has been given for the deal that will boost Germany as a distribution hub for Russian gas in western Europe and which has also been criticised by other EU members including Italy.
"For Germany, this project remains purely a matter of economics," Gabriel said. "We're in favour of diversifying gas supply sources and it is up to the German market and firms to decide where the gas comes from."
The European Commission, the EU's executive arm, has said the Nordstream pipeline risks concentrating 80 percent of the bloc's Russian gas imports on one route and will now look into whether the project meets European laws.
Russian energy giant Gazprom announced in early September a shareholders agreement with the German groups BASF and E.ON, France's Engie, Austrian OMV and Anglo-Dutch Shell to begin work on Nordstream 2.