Mr Pompeo was speaking after a strongly worded statement issued by the Association of Southeast Asian Nations (ASEAN) insisting China must abide by international laws. China claims sovereignty over the South China Sea, regularly encroaching on waters claimed by neighbours Brunei, Indonesia, Malaysia, the Philippines, Taiwan, and Vietnam.
Numerous uninhabited islands have been fortified by the superpower in recent years and the region has been the scene of a number of tense stand-offs between Chinese forces and US navy vessels.
ASEAN’s statement sought to “further reaffirm the importance of maintaining and promoting peace, security, stability, safety and freedom of navigation and over-flight above the South China Sea, as well as upholding international law”.
The statement also referred to the importance of the United Nations Convention on the Law of the Sea (UNCLOS) signed in 1982 as a mechanism for resolving disputes.
Mr Pompeo tweeted: “The United States welcomes ASEAN Leaders’ insistence that South China Sea disputes be resolved in line with international law, including UNCLOS.
“China cannot be allowed to treat the SCS as its maritime empire.
“We will have more to say on this topic soon.”
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China has repeatedly denied all accusations of a cover-up in its handling of the coronavirus crisis.
Speaking earlier this month, Tobias Ellwood MP, a member of the new Parliamentary organisation the China Research Group chaired by party colleague Tom Tugendhat, highlighted the region as a major flashpoint.
He told Express.co.uk: “There are three areas where China is advancing: economically, through the One Belt, One Road initiative, technologically, through its push with Huawei, tying people into that, and then, of course, militarily.
“Ultimately they are creating fortresses across the South China Sea and nobody is challenging them on that, despite international law saying otherwise.”
Beijing was effectively trying to “cordon the region off”, Mr Ellwood said.
He added: “Once they have got a military presence there they then can use that to expand their own footprint to challenge anybody that comes through.
“It’s getting more and more aggressive – we send ships through occasionally but they are treated with such hostility that you can easily see a minor conflict spiralling out of control.
“China covets superpower status but avoids any sense of duty to uphold the core values that we enjoy – freedom, democracy, rule of law etc.
“What it is doing is promoting a competing vision, subtly forcing nations to choose sides, the authoritarian system of control versus ours.
“They are utilising Huawei and other things to ensnare small countries into its web of influence and we are seeing this in the South China Sea as well.”