Gallas, suffering from a recurrence of a calf muscle injury which has kept him on the sidelines for nearly two months, took part in a light training session at France's camp in Tignes.
The 32-year-old, who arrived in the French Alps resort on Saturday three days before his team mates, is the reason why coach Raymond Domenech named a provisional 24-man squad instead of the official 23.
Domenech, who has until June 1 to take a player out, is hoping his most reliable central defender will be able to make the trip to the June 11-July 11 finals in South Africa.
The coach, who will be replaced by former France defender Laurent Blanc after the World Cup, spent 45 minutes during the 80-minute session talking to holding midfielder Lassana Diarra.
The Real Madrid player felt unwell during a hike up one of Europe's largest glaciers overlooking Tignes, at the foot of which the France players spent the night.
"He did not train because he is still a bit tired," a team spokesman said.
On Thursday morning, before coming back down to Tignes, the players were introduced to biathlon, a mixture of cross-country skiing and shooting popular in France.
Central defender Sebastien Squillaci, who could be an option if Gallas were ruled out, arrived in Tignes on Thursday, a day after helping Sevilla claim the Spanish King's Cup with a 2-0 win over Atletico Madrid.
The France players, cheered on by some 200 fans, looked relaxed during training on a gorgeous day in this scenic ski village surrounded by rugged snow-capped peaks.
The former world and European champions will play friendlies against Costa Rica, Tunisia and China before heading for the World Cup, where they face hosts South Africa, Mexico and Uruguay in Group A.
