Australian Webber, who will retire from Formula 1 when this season finishes, has claimed that it is a gamble for Ferrari to pair two former world champions together for the first time in six decades.
However, he does not feel that Raikkonen and Alonso will drive together for long, as he has suggested that Ferrari will pursue Vettel, a three-tme world champion and the current leader of the drivers' standings, when the German's Red Bull deal ends in 2016.
"There are so many reasons why it's a bit of a gamble to help Ferrari," he told Sky Sports News.
"[It will be] two years for probably both of them actually I think. And then what they do after that obviously [is] pick Seb up off the back of Red Bull and they keep moving from there.
"But it's a very short-term aggressive statement from Ferrari to put the team at the front."
Raikkonen was the last person to lift the drivers' title for Ferrari when he raced for them previously in 2007, while Alonso is a two-time world champion from his first spell at Renault.