SYDNEY (REUTERS) - The leader of the Federated States of Micronesia has urged the Solomon Islands not to sign a security pact with China, saying he had "grave security concerns" and feared the Pacific could become embroiled in war between China and the United States.

The prime minister of the Solomon Islands, Mr Manasseh Sogavare, said on Tuesday (March 29) a security agreement with China was ready for signing but he did not disclose its details and he rejected concern by Australia, New Zealand and the United States that it would undermine regional security.

"My fear is that we - the Pacific Islands - would be at the epicentre of a future confrontation between these major powers," Micronesia's president, Mr David Panuelo, wrote in a letter to the leader of the Solomon Islands, according to a copy seen by Reuters on Thursday.

"It's not an impossible fear; it has happened before. Both the Federated States of Micronesia and Solomon Islands were the battlegrounds during World War II," Mr Panuelo wrote, noting that the United States and China were increasingly at odds.

Micronesia has defence ties with the United States as well as a diplomatic and economic relationship with China, he said.

But he said the security pact Mr Sogavare was preparing to sign was unprecedented, and could fuel fragmentation of the Pacific islands so they became tools of great power rivalry.

The problem of climate change would be replaced by "all-too-real concerns about a war in our backyards", he wrote, pointing to the conflict in Ukraine.

An Australian defence official said Australia's navy would change its patrol patterns if the Solomon Islands formed a military agreement with China, because of the close proximity to the Australian mainland.

"It does change the calculus if Chinese naval vessels are operating from the Solomon Islands," Lieutenant-General Greg Bilton, chief of joint operations, told reporters.