Peter Sauber has confirmed that his team's much-hyped partnership with 1997 world champion Jacques Villeneuve is far from harmonious at present, but is determined not to make matters worse ahead of the start of the European F1 leg.

Villeneuve issued a statement thinly criticising the Swiss team after his testing schedule was altered on Thursday, prompting insiders to speculate that the relationship was close to breaking point. While neither driver nor team is willing to make the move towards divorce, it would appear that the next problem could be the last in what was billed as a marriage made in heaven for Sauber, and a conveniently low-key return to the top flight for Villeneuve.

"The partnership between Jacques Villeneuve and Sauber Petronas is currently at a difficult point," Sauber told news agency Reuters, "but to keep from straining the relationship any further, I would prefer not to make any further comments at the moment."

The charismatic team boss attempted to explain the thinking behind the revised test schedule, following Villeneuve's suggestion that the changes had badly hampered his preparations for the San Marino Grand Prix in two weeks, and prevented him from fully exploring some developments that he had been looking forward to trying since the opening round in Australia. Sauber has not tested during the three 'flyaway' events that started the year.

"The objective of our test in Barcelona was to evaluate new aerodynamic components," Sauber said, "Our times were so slow and inconsistent on Wednesday that the engineers were not certain about the cause. It was therefore decided to continue the test with Felipe Massa in order to have another reference."

While Massa opened his account with two points in Bahrain last weekend, Villeneuve has yet to score, although he came close to eight place in round three. Following on from three pointless performances with Renault at the end of 2004, many are suggesting that the 1997 world champion should get out of F1 while he still has some reputation to fall back on.

Sauber, however, has steadfastly refused to comment on the driver change rumours which, amongst the hearsay, have suggested that BAR tester Anthony Davidson, as well as either of Red Bull Racing's 'juniors' - Christian Klien and Vitantonio Liuzzi - could find their way into his squad.