Vattenfall German grid sale delayed to May-sources

* Binding offers due in May - sources

* Goldman Sachs, D. Bank, Allianz group still in - sources

* Utility-led group also in - source

* Regulator says set revenue cap, efficiency parameters

By Peter Dinkloh and Philipp Halstrick

FRANKFURT, March 30 (Reuters) - The sale of Swedish utility Vattenfall's [VATN.UL] high-voltage power grid in Germany has been delayed for a third time and is now scheduled for May, sources close to the matter told Reuters.

The sale of the eastern German long-distance grid -- a vital piece of German infrastructure worth around 1 billion euros ($1.3 billion) -- has been beset with difficulties.

Obtaining financing amidst the credit crisis has been hard and regulatory details are emerging only now.

"Binding offers are due in May," said one person with knowledge of the matter. The person declined to be identified because the process is confidential.

Vattenfall as well as larger peer E.ON (EONGn.DE) are selling their long-distance power grids due to pressure from the European Commission, the executive arm of the European Union, and as regulation cuts returns from the business.

Germany's Federal Network Agency said on Monday it had set the so-called revenue cap -- the amount of revenue utilities may generate with their grids -- for the four network operators and informed utilities of this at the end of March.

The sales process was practically halted as utilities wrangled with the regulator about revenue and efficiency parameters. Bidders need those details to calculate the value of the business and their potential bids.

Vattenfall's German unit, E.ON, RWE (RWEG.DE) and Energie Baden-Wuerttemberg (EBKG.DE) run the country's four high-voltage transmission grids.

"Now we are moving ahead," said one source with knowledge of the matter.

Among the potential suitors are a consortium led by a utility and a consortium consisting of Goldman Sachs (GS.N), Deutsche Bank (DBKGn.DE) and Allianz (ALVG.DE), said two people.

In addition there are several parties that are willing to take a minority stake in the business, said one person.

A spokeswoman for Vattenfall said the company still plans to sell the business in the first half of 2009, declining to comment further.