The Americans got the better of Slovenia 4-1 in Portoroz and Belgium beat visitors Croatia 3-2 in Bree. Fellow top side Russia also made the July 10/11 last eight clashes with a 4-1 victory over Australia in Moscow.

Japan however lost to Argentina when Ai Sugiyama retired in the third set with cramps to Paola Suarez to lose 6-7, 6-3, 7-6 and give Argentina a 3-0 winning lead.

Lisa Raymond bounced back from her opening day loss to put the United States through at the expense of Slovenia.

Raymond, who lost the opening match of the tie to Tina Pisnik on Saturday, beat Katarina Srebotnik 5-7, 6-3, 6-4 to give the Americans an unassailable 3-1 lead.

Srebotnik led 4-3 with a break of service in the final set but Raymond managed to win the last three games to snatch the victory.

The Americans now face Austria in their July 10/11 last eight tie.

Venus Williams, who said she plans to be available for the quarter-final, easily beat Slovenian number one Pisnik 6-3, 6-1 in the first Sunday singles.

Belgium's Clijsters, out for five weeks with an injured left wrist, celebrated her comeback by winning both singles to oust Croatia.

On Saturday, Clijsters beat Jelena Kostanic 6-1, 4-6, 6-1 and then on Sunday beat Karolina Sprem 6-1, 6-3. Els Callens clinched the tie for Belgium by beating Kostanic 6-2, 3-6, 6-4 for a 3-1 winning lead.

In other matches, Austria got the better of Slovakia 3-2, France beat Germany 5-0 and Spain beat Switzerland 3-2. Italy lead the Czech Republic 2-1 in Lecce with the final singles and doubles to be played on Monday because of rain.