FIA race director and technical head Charlie Whiting told reporters at the weekend's Bahrain Grand Prix that the delay was not unusual, however.
“Pirelli wanted the targets that they were asked to achieve to be put into the contract. They want more specific items in the contract regarding testing. They really just want a guarantee of testing,” he said.
“If we are going to set them targets, they want the tools with which to achieve those targets. Those are really the only points. I think everything else is sorted but they just want this guarantee of tests.
“We've put it into the regulations but they'd like a little comfort and also the possibility to test with their own car... I think it's all quite achievable in the short term,” added Whiting.
The new sole supplier agreement, already agreed with the commercial rights holder but needing to be signed off by the FIA, is for three years.
Formula One is preparing for major rule changes next season aimed at making cars faster, harder to drive and with more downforce.
As part of those plans, wider tyres will be subjected to heavier loading and faster cornering speeds.
Teams are currently subject to strict limits on track testing before and during the season but the regulations now allow for 12 days of tyre testing.
Pirelli is seeking clarity on what kind of car and which drivers could be used.
“The key for 2017 is that we have a very clear written mission of what it is they expect us to deliver...and allow us then to be in a condition to actually deliver that,” Pirelli motorsport director Paul Hembery said earlier in the year.
Original source: Why hasn't Pirelli signed F1 contract?