MANILA (UPDATE) — Sen. Francis "Kiko" Pangilinan is running for vice president in the 2022 elections, sources told ABS-CBN News on Thursday.

Pangilinan will be the running mate of Vice President Leni Robredo, who earlier in the day declared she was vying for the top job in next year's polls.

"Sen. Kiko was chosen because he is a reliable partner at pareho sila ng prinsipyo, pareho sila ng paninindigan (and they have the same principles and stance on issues)," a source told ABS-CBN News.

Pangilinan, 58, is president of once-ruling Liberal Party chaired by Robredo. The party's chairman emeritus Benigno "Noynoy" Aquino III succumbed to kidney failure last June.

The senator and Robredo have opposed several key policies of President Rodrigo Duterte's administration, including the war on drugs, stance on the West Philippine Sea, and push for death penalty.

Pangilinan also led the campaign bid of opposition slate Otso Diretso in the 2019 midterm elections.

Opposition coalition 1Sambayan, which nominated Robredo for the post, recommended a different running mate, its convenor and retired Supreme Court Senior Associate Justice Antonio Carpio said.

“Her choice is not what we recommended. But under our process, she can nominate somebody else other than our choice,” he told ANC.

Carpio said he understood Robredo’s choice “because you have to look at the, of course, the contribution of your vice president.”

“You know, you have to think of also the regional balance. You cannot get a candidate from your own region. So there are many factors that go into this decision,” he said.

Asked if he was happy with Robredo’s choice, Carpio said, “Of course I’m happy with the choice. We have a very strong team.”

“There is a regional balance. Both of them have won public offices.... I think we have a good team. We have a strong ticket,” he added.

Pangilinan has yet to respond to requests for comment.

Pangilinan's vice presidential bid will be announced at 4 p.m., when he and Robredo file their certificates of candidacy, a source from the Liberal Party said.

Former Ifugao Rep. Teddy Baguilat will replace Pangilinan in the opposition's Senate slate, the source said.

Pangilinan will contend with former Manila Mayor Lito Atienza, Dr. Willie Ong, Sen. Christopher "Bong" Go, and Senate President Vicente Sotto III for the second highest elected post in the country.

Sotto is an in-law of Pangilinan's wife, actress Sharon Cuneta.