Cristiano Ronaldo resumes training
The duo have missed both of Portugal's pre-finals friendlies so far - a 0-0 draw with Greece and Friday's 1-0 win over Mexico.
Ronaldo has been struggling with persistent knee injuries, while Meireles has suffered with a thigh problem.
However, a statement on the Portuguese Football Federation's website on Saturday explained that both would return to training with the rest of the squad.
One worry for coach Paulo Bento is the fitness of central defender Pepe, who has been troubled by a calf injury and continues "individual rehabilitation and specific exercises".
Portugal have one more friendly, against Republic of Ireland in New Jersey on Tuesday, before their World Cup campaign begins.
Following that game, Bento and his squad will fly out to Brazil and begin final preparations for their opening Group G fixture against Germany on June 16.