Fed Cup debut for Maria

The U.S. Open champion will be joined by Nadia Petrova, Svetlana Kuznetsova and Elena Dementieva, forming a powerful Russian line-up for the two-day tie in Moscow on April 21-22.

"Yes, all four of our girls have agreed to play against Spain," president of the Russian tennis federation Shamil Tarpishchev, who is also their Fed Cup captain, told Reuters.

"Of course, anything can happen between now and next April but barring any injuries, they all will be in the team."

All four Russians are now in Madrid, taking part in the season-ending WTA Championships, which began on Tuesday.

World number two Sharapova is riding on a three-tournament winning streak after her triumphs at the U.S. Open, Linz and Zurich and has a good chance of clinching the number one spot.

There have always been doubts in the Russian media over whether Sharapova would ever play for her country, but the Florida-based teenager made herself available for Russia's Fed Cup team last month.

"I'm really excited to make my first appearance in the Fed Cup for my country and it is great to be playing the tie in Moscow," the 19-year-old said on her website.

"Hopefully, myself and the team will put up a strong showing against Spain, who have a good team."

Kuznetsova, Petrova and Dementieva are all in the world's top eight, occupying the fourth, fifth and eighth spots respectively.

Russia will try to regain the Fed Cup title they won in 2004 and 2005. This year they lost to Belgium in the quarter-finals.