Institutional investors led by U.S. energy transmission developer Anbaric Transmission are interested in pumping up to 4 billion euros ($5.2 billion) into linking German offshore wind farms with the mainland.

Anbaric could act as an intermediary for potential European and U.S. investors willing to help finance up to four offshore network link projects of grid operator TenneT, an Anbaric spokesman said on Monday.

"That would be a reasonable first package," he said.

A spokeswoman for TenneT TSO, the German arm of Dutch state-owned firm TenneT , said there had been "an exchange of information, but no more".

Anbaric earlier this month denied it was planning to bid for Tennet's German unit.

TenneT bought Germany's biggest power grid in 2009. It is used mainly by E.ON .

The Anbaric spokesman said on Monday that TenneT would remain the operator as Anbaric had no interest in that role.

TenneT has come under political and financial pressure over delays in linking off-shore wind farms with the mainland.

Germany aims to boost renewables to 35 percent of its power output by 2020, with over 10,000 megawatts of offshore capacity installed by then.

A fresh setback to the process came at the weekend, when one of the biggest foreign investors in German wind energy, Denmark's DONG Energy , said it has frozen plans to develop the Borkum Riffgrund 2 wind farm on the North Sea coast of Germany.

DONG said TenneT had failed to provide a fixed date for when offshore power cables could be installed.

TenneT has defended its record repeatedly, saying it has invested billions and is being overstretched by taking on full costs of investment in offshore cable links on its own. It has called on the German government to clarify long-term plans and liabilities.

On Monday the German parliament was due to discuss a proposed bill to clarify issues related to liability in the case of offshore wind farms.

"We need a reliable legal framework for German offshore soon," utility RWE Innogy said in a statement.

Its Nordsee Ost project has been delayed by between 18 and 24 months due to delayed links to transmission networks onshore.

(Reporting by Tom Kaeckenhoff and Rene Wagner, writing by Vera Eckert; editing by Jason Neely)