BERLIN (AFP) - Merger talks between Europe's biggest carmaker Volkswagen and luxury sportscar manufacturer Porsche were suspended Sunday, amid a rift between the two German auto giants.

There is currently "no clear constructive attitude" on the part of Porsche, a Volkswagen spokesman told AFP. "Therefore there is no point in having further talks at the moment," he added.

Dialogue between the two parties had been "suspended," he said.

For their part, Porsche played down the rift.

"The negotiations, which began last week, are continuing in a completely normal fashion," the firm said.

A meeting planned for Monday has however been cancelled, Porsche confirmed.

The two sides have been at loggerheads following comments on Thursday by Ferdinand Piech, head of VW's supervisory board. He said Porsche had to cut its debt mountain -- valued at roughly nine billion euros (12 billion dollars) -- before any merger.

The two auto giants agreed on May 6 to begin merger talks, giving themselves four weeks to agree a tie-up.