SYDNEY, Aug 6 (Reuters) - President Joe Biden told a forum of Pacific island leaders in a recorded message on Friday that their countries would benefit from U.S. donated COVID-19 vaccines distributed without political strings.

China has in recent years become a more assertive competitor for influence in the Pacific, prompting the United States and its allies to warn island nations against becoming indebted to Beijing. China has consistently said it engages with Pacific nations with mutual respect and on an equal footing.

Biden told the Pacific Islands Forum that the U.S. would donate "half a billion" doses of the Pfizer COVID-19 vaccine to the global COVAX vaccine-sharing programme starting this month, some of which will flow to the Pacific.

"We are not attaching any strings or conditions to these doses - this is about saving lives," Biden told the online forum, consisted of leaders from several nations including Fiji, Papua New Guinea, Australia and New Zealand.

Although some Pacific island nations have been able to use their natural borders to keep the coronavirus at bay, others, including Fiji and Papua New Guinea, are battling significant outbreaks.

Biden told the forum in a recorded message that the U.S. was committed to dramatically reducing emissions by 2030, an issue pertinent to low-lying island nations, while also helping vulnerable communities build resilience.

He said the U.S. would remain engaged in the region.

"A free and open Indo-Pacific is vital to each of our nations' security and prosperity and to all our shared futures," Biden said.

The Pacific Islands Forum is traditionally the Pacific's most influential regional body, although nearly one-third of its 18 members said this year they were leaving the group over a leadership dispute.