"I don't know if he will stay or not, and neither he nor the team know either," Mourinho said at an awards ceremony in Lisbon.
"There are no doubts between us, he knows what I think and I know what he thinks," added the Portuguese, according to the Real website.
"As long as he is our player, and it's possible that he will stay another season, he will contribute.
"If he stays I'll be delighted and he will come to the U.S." on our pre-season tour.
Mourinho included 2007 World Player of the Year Kaka in his squad for Real's friendly at Benfica later on Friday but the 30-year-old is widely expected to move on after three largely disappointing seasons in the Spanish capital.
Mourinho was also asked about Real's Turkey midfielder Nuri Sahin, who has barely featured since joining from Borussia Dortmund a year ago.
"Nuri is living in the grey zone and if he gets a good chance to play we believe it's better for him to leave and play elsewhere this season," he said.
