China on Friday hit back at US President Barack Obama's latest warning over the country's actions in the South China Sea, reiterating its stance in maintaining stability and peace in the region and called on the US to respect its efforts.

"I think it is clear who has the biggest size and muscle in the world," said Chinese foreign ministry spokeswoman Hua Chunying in a daily briefing, responding to Obama's warning that China should not "elbow aside" countries it is in dispute with in the South China Sea at a town hall event on Thursday during his visit in Jamaica, hinting at China's construction work on some islands and reefs.

"Where we get concerned with China is where it is not necessarily abiding by international norms and rules and is using its sheer size and muscle to force countries into subordinate positions, and that is the concern we have around maritime issues," Obama said.

"Just because the Philippines or Vietnam are not as large as China doesn't mean that they can just be elbowed aside," he said.

China made a rare explanation on Thursday of its maintenance and construction work on some Nansha islands and reefs, where it claims indisputable sovereignty.

Hua said that China's purpose is to strengthen the functions of those islands and reefs, and improve the working and living conditions of its personnel stationed on them.

The construction will help the islands and reefs to provide comprehensive services to meet various civilian demands besides satisfying the need of necessary military defense.

It will also help China to better carry out international responsibilities in maritime search and rescue, disaster prevention and mitigation, marine science and research, meteorological observation, navigation safety, fishery production service and other areas, said Hua.

Washington has been targeting China's construction work in the past year, starting with a proposal in August last year, which calls for a freeze of all "provocative acts" in the South China Sea.

US Secretary of Defense Ashton Carter expressed "concerns" over the construction work during his visit to Japan this week, before Obama's speech ahead of the Summit of the Americas in Panama.

In a bolder statement, US State Department spokesman Jeff Rathke said Thursday in a press briefing that Washington is concerned that China "might militarize outposts on disputed land features of the South China Sea."

The accusations came after China and Vietnam, which have territorial disputes in the South China Sea, made progress through a joint communiqué released on Wednesday.

In the document, the two countries reaffirmed that they would control maritime disputes, comprehensively implement the Declaration on the Conduct of Parties in the South China Sea, reach a Code of Conduct through negotiations in early date, and avoid actions that may complicate and escalate the disputes.

China should be prepared for further moves from the US as it is unwilling to see a more active Chinese military presence and possible encounters in the South China Sea, Xue Li, a research fellow with the Chinese Academy of Social Sciences, told the Global Times, adding that Washington hopes to pressure China into a halt on the project as it is now the best construction season before typhoons arrive in the summer.

Hua on Friday called the US to respect the efforts made by China and ASEAN countries in resolving the South China Sea issue, and genuinely play a "positive, constructive and responsible role" in promoting peace and stability in the region.

Despite the accusation, Obama was careful to emphasize that China's economic power plays a positive role in the world, and said the US "welcomes" global aid investments during the same speech in Jamaica. "We should be more fearful of a poor collapsing China than a China that is participating in the world marketplace," he said.

"It is important now for China to send signals to the US that it should withdraw from intervention and focus on cooperation in regional security and economic development. China can make greater international contribution judging from the wide approval of the Asian Infrastructure Investment Bank," said Xue.

He added that it is improper for the US to exaggerate the military functions of the facilities on the islands.

Hua warned the US on Thursday "not to adopt double standard, keeping silent about long-time construction works by certain countries on the illegally occupied islands and reefs of China's Nansha Islands, yet pointing the finger at China's normal activities on its own territory."

It is unlikely for China to halt construction as the islands could help China push forward dialogues and negotiations in the joint development of the region, said Xue.

Agencies contributed to this story