BOGOTA, Colombia (AP) — Colombian Vice President German Vargas Lleras has offered his resignation amid speculation he'll seek the country's top office in next year's election.

Vargas Lleras delivered a letter to Congress Wednesday night asking lawmakers to relieve him of his duties. A vote is expected next week. Sitting officials must resign by May in order to be eligible to run in the May 2018 election.

Polls show the famously hot-tempered politician is one of the front-runners to succeed President Juan Manuel Santos after having overseen the biggest infrastructure buildout in decades.

But he's mistrusted by many of Santos' supporters and being courted by some right-wing opponents because of his lukewarm support for a peace deal with leftist rebels.

Santos has already tapped former police chief Oscar Naranjo to replace Vargas Lleras.