MANILA -- The Philippines can tap other bilateral partners outside of the 18 governments that support a UN investigation into President Rodrigo Duterte's war on drugs, his spokesman said Monday.

Rejecting loans and grants from those backing Iceland's call for an inquiry will have no effect on the economy, Presidential Spokesman Salvador Panelo said.

"There are other bilateral partners and institutions, and other countries outside of the 18 offering the same and no better rates than these countries. Madaling sabi, walang epekto sa atin (The point is, it will have no effect on us)," he told reporters.

"It will not dramatically, even slightly I think, impact on our economy," he said.

Opposition lawmakers have warned the Duterte administration against rejecting aid from the 18 countries as this might isolate the Philippines from the international community.

• Opposition solon warns vs rejecting loans from states critical of drug war
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Duterte has issued a memorandum suspending loans and negotiations involving 18 member-countries of the United Nations Human Rights Council, which in July approved Iceland's resolution to compile a report on Manila's 3-year narcotics crackdown.

The Palace initially denied such a memorandum but Panelo confirmed the order Monday saying the President might have forgotten it due to "lapse of memory."

• Palace confirms shunning foreign aid, cites Duterte 'lapse of memory' for initial denial

Panelo said existing grants and loan agreements with other countries would not be affected since these were already being implemented.

Of the 18 countries that backed the Iceland resolution, Panelo said only the United Kingdom has a 21 million euro (P 1.20 billion) loan offer to the Philippines that "will not affect our economy."