Argentine President Mauricio Macri says he's choosing the leader of the largest opposition bloc in the Senate as his running mate in October's presidential election.

Macri said Tuesday on Twitter that he chose Miguel Angel Pichetto because Argentina will "need to build agreements."

The conservative Macri is seeking re-election amid a recession, a devaluation of the currency and one of the world's highest inflation rates.

Leftist former president Cristina Fernández surprised Argentines last month when she announced that she'd try to return to power by running as vice president on the ticket with her former chief of staff Alberto Fernández.

Pichetto was allied with Fernández during her 2007-2015 administration, but has since broken with her and headed a more moderate opposition faction.