The Catalan giants confirmed on their official website that the Argentine would pen the deal “in the coming weeks”.
Messi’s current deal runs until June 2016 and the new agreement will keep him at the Nou Camp beyond his 31st birthday.
The forward has enjoyed an extraordinary year, even by his own remarkable standards, netting his 89th and 90th goals of 2012 last weekend.
According to reports, he is also in contention to claim a fourth successive FIFA Ballon d’Or crown, being named on a three-man shortlist alongside Cristiano Ronaldo and teammate Andres Iniesta.
A statement on the Barcelona website read: “This news means that FC Barcelona have secured ties with three of their most important players. Over the course of the next few weeks, Carles Puyol, Xavi Hernandez and Leo Messi will all be signing their respective new contracts.”