A consortium of six of the Philippines' biggest conglomerates on Tuesday dropped a proposal to upgrade and operate the country's main airport, as the impacts of the coronavirus hit the viability of the $2 billion project.

Modernising the ageing and congested Manila airport was among the largest projects of President Rodrigo Duterte's $180 billion "build, build, build" planned infrastructure overhaul, his signature economic policy.

The consortium said it reviewed its plans in light of the impact of the coronavirus on global travel and proposed to the government changes to ensure the Ninoy Aquino International Airport (NAIA) project was viable.

"Unfortunately, the government indicated that it is not willing to accept most of the consortium's proposed options and the consortium can only move forward with the NAIA project under the options it has proposed," the group said in a statement.

The consortium comprised units of JG Summit Holdings Inc, Alliance Global Group Inc, Filinvest Development Corp, Aboitiz Equity Ventures Inc, Ayala Corp and LT Group Inc.

The withdrawal will be another blow to Duterte's hopes of bettering his predecessors and delivering on urgently needed infrastructure, with doubts over several other projects long before the coronavirus hit, and time running out before he must leave office in 2022.

The economic planning agency, which approves big-ticket projects including the NAIA upgrade, did not respond to requests for comment.

In 2018, the consortium proposed a 350 billion pesos ($7 billion) plan to modernise the over-stretched international airport and operate it for 35 years. It revised that offer a year later to a $2 billion, 15-year concession.

Airlines passengers suffer chronic delays because of congestion in Manila's airport. But operations have been minimal since March when the government implemented travel bans and lockdown measures to help contain the spread of the virus.

(Reporting by Neil Jerome Morales; Editing by Martin Petty)