Ahead of a big programme to prepare rubber for the new 2014 regulations, there had been speculation that Pirelli could opt for a driver who had race experience from last year.
However, Pirelli's motorsport director Paul Hembery made it clear on Wednesday that he was happy to keep the two youngsters on board, especially as a lot of 2014 work would be done on simulators.
"I read on Twitter that [Kamui] Kobayashi would be unveiled today as a test driver, but he won't," said Hembery at the official launch of Pirelli's 2013 plans in Milan.
"There is no reason to change what we have. We have had a great time with Jaime Alguersuari and Lucas di Grassi.
"We need to renew our contract [in F1] first, and then will look at the tyres and the compounds. There will be a lot more use of simulator, because we have worked extensively on tyre modelling. That is how we will focus on the changes for 2014."
Pirelli announced on Wednesday that former grand prix driver Jean Alesi has become a brand ambassador for the company.