Pressure is mounting on President Rodrigo Duterte's government to kickstart the delayed vaccine rollout, amid accusations its officials have bungled the procurement and delivery of jabs.

Beijing's donation of 600,000 doses of the Sinovac vaccine will arrive Sunday, the Chinese embassy in Manila said Thursday. The military is supposed to receive 100,000 of those doses.

The announcement comes days after the Philippine drug regulator gave emergency approval to CoronaVac despite widespread misgivings over its safety and effectiveness.

It is still not clear who will receive the first injections -- or even when.

Duterte has said he wants soldiers to be among the first to be inoculated, but health authorities said Thursday the allocation and rollout were still being "evaluated".

What is certain is members of the military will be vaccinated eventually -- whether they want it or not.

"To get inoculated or not is not an option for the members of the Armed Forces of the Philippines. It is a duty", said spokesman Major General Edgard Arevalo.

Vaccines will free but if soldiers want to choose a brand not in the military's stockpile then they will have to pay for it, added Arevalo.

Those who refused to be inoculated could be disciplined.

Soldiers most at risk of exposure to the virus will be prioritised and will have to take the vaccine available at the time, even if that is CoronaVac.

It was better than "not having a protection at all", Arevalo said.

The order comes after Pentagon officials said roughly one-third of US soldiers declined a coronavirus vaccine, as the government taps troops to help nationwide-inoculation.

CoronaVac is the third vaccine approved for emergency use in the Philippines. But the Food and Drug Administration said it was not recommended for health care workers due to its comparatively low efficacy.

Although trials in Turkey found CoronaVac to be 91.25 percent effective, other, more robust trials in Brazil only demonstrated an efficacy rate of around 50 percent.

The government is in talks with seven vaccine makers, including Sinovac, in the hope of securing enough doses to inoculate 70 million people -- about 60 percent of the population -- this year.

But the bulk of the supply is not expected to start arriving until the second half.