MANILA - The Philippines and Japan signed on Friday the first tranche of a 104.5 billion yen (P51.3 billion) loan for Metro Manila's first subway, one of the centerpieces of President Rodrigo Duterte's infrastructure overhaul, according to a government statement.

The subway will begin partial operations by 2020, said Finance Secretary Carlos Dominguez, who signed the loan along with Japan International Cooperation Agency chief representative Yoshio Wada.

Dominguez called the subway the "biggest single project" under the P8 trillion program dubbed "Dutertenomics."

Once completed, the subway will have 14 stations and will run from Mindanao Avenue in Quezon City up to the Ninoy Aquino International Airport.

"The timely completion of the subway project will crown the aggressive infrastructure program the administration of President Duterte has initiated," Dominguez said.

"It will likewise crown the achievement of the economic diplomacy the Duterte administration has undertaken," he said.

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Japan has increased engagements with the Philippines since the time of Duterte's predecessor, Benigno "Noynoy" Aquino, as Tokyo and Manila faced separate maritime disputes with Beijing.

In a rare diplomatic gesture, Japanese Prime Minister Shinzo Abe visited Duterte at his home in Davao City last year.

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