Despite loud criticism from some quarters of the paddock, notably the Red Bull camp, it was expected that F1's official supplier would merely tweak the compounds of its 'soft' and 'hard' compounds for Barcelona.
But Pirelli announced on Thursday that, in fact, only the hard tire will change.
"This latest version of the hard compound is much closer to the 2012 tire, with the aim of giving the teams more opportunity to run a wider range of strategies in combination with the other compounds, which remain unchanged," said Paul Hembery.
Pirelli did not mention reported plans to supply an extra set of more durable tires to teams on Friday mornings, instead reiterating the current rules stipulating six sets of prime and five sets of option tires per driver.
Reuters news agency quoted a spokesman as saying the issue is awaiting the FIA's approval.