Beijing faces pressure over its island-building in the South China Sea during high-level Asian security meetings this week that will include the top US and Chinese diplomats.
China is expanding tiny reefs into islands and topping some with military posts to reinforce its disputed claims over the strategic sea, fanning fears of a regional arms race and possible conflict.
Southeast Asia's human-trafficking problem and concerns over North Korean missile launches are also expected to be among the issues discussed at the talks in Kuala Lumpur.
But a senior US State Department official said the sea row will be at the "centre" of the three days of foreign minister meetings starting Tuesday, an annual security dialogue hosted by the 10-member Association of Southeast Asian Nations (ASEAN).
"The ASEANs, like us, are concerned about the scale, the scope, the pace, and the implications of China's reclamation work," the US official said.
Secretary of State John Kerry and his Chinese counterpart Wang Yi will attend the ASEAN Regional Forum (ARF), along with foreign ministers from Southeast Asia, Japan, the Koreas, and other nations.
ASEAN members Vietnam, the Philippines, Malaysia and Brunei all have various claims to the South China Sea, as does Taiwan.
But Beijing claims nearly all of it, and its neighbours complain the land reclamation violates a regional pledge to avoid provocative actions.
The dialogue is an opportunity for ASEAN and others "to express directly to the Chinese" their concerns, the US official said.
ASEAN has grown increasingly impatient, but Beijing adamantly rejects criticism, claiming "indisputable" sovereignty over nearly all of the waterway, believed to hold important oil and gas reserves.
Washington has warned the tensions could impede freedom of navigation in what is a major route for international trade.
Malaysian Foreign Minister Anifah Aman told reporters Friday there had recently been "important progress" in talks between ASEAN and China toward a "Code of Conduct" (COC) at sea, a set of rules meant to avoid conflict.
However, Aman's statement seemingly contradicts recent comments made by the Philippines secretary of foreign affairs, who told a court in the Hague last month that Beijing had spent years preventing a potential COC deal from being ironed out.
"China's intransigence in the 13 years of subsequent multilateral negotiations has made that goal nearly unattainable," Albert Del Rosario told the Permanent Court of Arbitration.
A protestor rallies outside the Chinese Consulate in Manila on July 7, 2015, denouncing China's claim to most of the South China Sea including areas claimed by the Philippines.
Analysts concur, saying Beijing has long worked to frustrate progress while building up its presence.
"China's leaders will not sign, or if they sign they will not abide by, an enforceable COC whose implementation would seriously constrain their freedom to do as they please," Donald Emmerson, a Southeast Asia expert at Stanford University, wrote recently.
The "time has come to abandon ASEAN's entrenched mirage" of a meaningful COC, he said.
Kerry is expected to push hosts Malaysia to step up efforts to fight human-trafficking after Washington last week controversially lifted the country out of the lowest tier in its annual report card on the scourge.
Southeast Asia was seized earlier this year by a refugee crisis after a Thai crackdown on people-smuggling left thousands of migrants from Bangladesh and Myanmar stranded at sea.
Along with Thailand, Malaysia was found to have brutal trafficking camps on its soil.
Southeast Asian countries blamed Myanmar over the persecution of its Rohingya minority, which drives many into trafficking rings.
It was not clear whether ASEAN member Myanmar would face significant pressure over the issue in Kuala Lumpur.
Kerry also is due to meet with his Turkish counterpart as both sides grapple with the threat posed by the Islamic State.
There is also the possibility the top North and South Korean diplomats could hold a brief and rare meeting.
Perennial tensions between the Koreas remain high, with nuclear-capable Pyongyang believed to be preparing for a long-range rocket test.