Sao Paulo, Brazil - Three-time world footballer of the year Ronaldo could be fit enough to play for Brazil at the 2010 World Cup finals in South Africa, his team doctor told German Press Agency dpa.

Although Ronaldo will be nearly 34 when the tournament takes place, he should be physically strong enough to play at the highest level, Corinthians doctor Joaquim Grava said.

"If he continues to work in this rhythm, doesn't get injured and nothing unpredictable happens he is absolutely in a position to take part at the World Cup, without any doubt," Grava said.

Ronaldo, who made a comeback early last month from a serious knee injury, scored his fifth goal in seven matches Tuesday to help Corinthians beat Ituano 3-0 and secure a spot in the semi-finals of the Sao Paulo state championship.

The striker was suffering no problems from the left knee but is physically not in best shape, with physical performance at around 40 per cent of the rest of his team, the doctor said.

"He will gain the rest during the next few games. He will probably reach 100 per cent by mid May," he said.

Ronaldo missed more than a year after surgery for a torn knee ligament and has also been fighting weight problems. Local media estimate he weighs around 90 kilograms at present, but Grava said this was not the key to his fitness.

Often weight can increase although the fat ratio is low. Ronaldo had gained strength, with a body fat ratio of 10.5 per cent which was "a normal level for a player," he said.

Grava also pointed out that other world-class players have put on weight in the course of their careers.

"Just compare the weight of Pele at the 1958 World Cup and the 1970 tournament, or the weight of (Franz) Beckenbauer when he started and at the end of his career," Grava said.

Even Ronaldo's age next year will be no obstacle, with a fit player able to play on to 36 or 38, Grava added.

Ronaldo has not played for Brazil since the 2006 World Cup, but coach Carlos Dunga has not ruled selecting the player if he returns to best form.

The striker has scored a record 15 goals at three World Cups, including eight in 2002 when he helped Brazil win a record fifth title. (dpa)