Swiss World number one Roger Federer will not play the first round of next season's Davis Cup.

Federer told a news conference on Wednesday that the decision had been "very difficult" but said his priority for 2005 had to be the defence of his number one ranking.

Switzerland are at home to the Netherlands for the tie in early March.

The 23-year-old, who won three grand slam tournaments in 2004, has been the driving force behind Switzerland's Davis Cup challenge since making his competition debut in 1999.

In 2001 Federer played in all three winning rubbers to earn the Swiss a first-round win over the U.S., a feat he repeated in ties against Morocco, France and Romania.

Federer said the decision to move the Davis Cup's first round to directly before the Masters Series tournaments in Indian Wells and Key Biscayne, had influenced him.

"Those two tournaments are very important," Federer explained. "The tennis year isn't just the four grand slams. When I won Indian Wells last year, I had the feeling that I'd made a big step forward."

Federer said the recent thigh muscle injury that ruled him out of this week's Paris Masters had also played a part in his decision.

"It's essential to get some rest during the season," he said adding he was confident of being fit again in time for this month's lucrative Masters Cup finale.

Federer, who carried the Swiss flag during the Athens Olympics opening ceremony, said he hoped to be back in the Davis Cup team for their next encounter.