"After the summer I will think and I will make a decision about what I will do next year," Alonso said in Bahrain.
But some say the 35-year-old is definitely no longer prepared to be a midfield runner, which could indicate why he has elected to skip Monaco this year in order to race at Indianapolis.
"Definitely. I want to win, I'm here to win," he said. "No more fifth or sixth.
"I think I'm really at the best of my career right now in terms of driving, so for next year there is only one target -- fighting for the world championship."
But his options for 2018 appear limited, with bridges burned at Ferrari and Mercedes and Red Bull having no vacancy.
Renault, however, could be an obvious choice.
Alonso won his only two titles for the French carmaker over a decade ago, and the newly-developing works outfit might now be seen as 'best of the rest' behind the top three teams.
Germany's Bild newspaper reports: "The French have a serious interest in the Spaniard and the first talks have already taken place.
"Renault wants to bring its veteran back and make him Nico Hulkenberg's teammate in 2018."
The Auto Bild publication has more details, saying talks took place in Bahrain on Saturday morning, involving Alonso's manager Luis Garcia Abad and Renault boss Cyril Abiteboul in the Renault hospitality area.
Renault did not comment.