As the US urges world leaders to ramp up action on climate change, the leader of one small island chain in the North Pacific Ocean has already got the message -- watching helplessly as rising seas slowly erode his birthplace.

The idyllic beaches on the island of Buoj where Marshall Islands President Christopher Loeak fished as a boy are already submerged, and the ever-encroaching ocean now threatens to wash away roads, schools and airstrips.

"The end of the island gets shorter every year. Some places we used to stand on the beach to fish are now in the water," Loeak, 60, told AFP.

Buoj is one of 52 islands in Ailinglaplap, an atoll that a Marshall Islands survey found was one of its most vulnerable to climate change.

"I have great attraction to Ailinglaplap," Loeak said in the capital, Majuro. "I can live on other islands, but I was born and raised there. I always think about going back there to live."

The Marshalls, an island nation of some 70,000 people about halfway between Australia and Hawaii, will have a rare moment in the international spotlight in September, when it hosts the annual Pacific Islands Forum.

Loeak said he wanted to use the opportunity to send a strong message to the world, particularly larger polluting nations, about the need for action to slow down climate change.

"We will not stop telling people that climate change is a real issue for humanity," he said. "We will be the first to feel it, but it will come to them and they should realise it."

The warning was echoed by Barack Obama in a landmark speech Tuesday, in which the US president dismissed climate change deniers and outlined steps aimed at making Washington a global leader in greenhouse gas reduction.

"We don't have time for a meeting of the Flat Earth Society," Obama said.

"Sticking your head in the sand might make you feel safer, but it is not going to protect you from the coming storm."

The impact of global warming is starkly evident in Ailinglaplap, with the Marshall Islands' senior climate change advisor Steve Why saying the majority of the atoll's shorelines were eroding.

"Infrastructure at risk of eroding includes three airstrips, roads, causeways and schools," he said.

Why and his survey team documented coastal erosion as an increasingly serious problem affecting many of the atoll's islands and noted the threat of rising sea levels to the entire country.

"Strong northeast trade winds since October 2012 have elevated sea levels three-to-six inches (7.6-15.2 centimetres), noticeably accelerating erosion on Ailinglaplap," he said.

About 1,700 people are scattered on the atoll's islands, which are barely a metre (three-feet) above sea level, even at their highest points.

A causeway linking some of the islands is disappearing, while salt water makes previously productive agricultural land useless.

Why said discussions with the community showed people wanted the infrastructure problems fixed, but they were reluctant to confront the worst-case scenario.

"Most conversations stalled as we envisaged what the future held -- over a three foot rise in average sea level during this century, and more beyond that," he said.

"(It's) not difficult to imagine what will happen over the coming decades while standing, talking, sleeping and raising one's family on land that is just a couple of feet in elevation above the high tide mark -- a line that is now always slowly moving inland -- when there isn't anywhere else that's easy to retreat to."

Loeak said the fate of the low-lying nation raised questions about the basic human rights of those affected by global warming, warning that if the islands were ultimately engulfed by the ocean, "we become refugees".

Loeak said that while he was happy to see world leaders such as Obama talking about climate change, it had not changed the fact that sea levels were continuing to rise in the Pacific.

And he said in the face of rising waters, his own fate was tied to that of the island.

"I will remain here until I die," he said. "If the water comes, it comes."