Palau's president has accused China of flouting the Pacific nation's maritime borders, raising concerns about research vessels lurking "uninvited" within its waters.
"We keep on raising flags and complaining about it, but they keep on sending them," said President Surangel Whipps Jr, the pro-US leader re-elected this week.
"They continually don't respect our sovereignty and our boundaries and just continue to do these activities," he told AFP from Palau's commercial centre Koror.
The most recent foray was detected earlier this week, Whipps told AFP on Tuesday evening, one day after claiming victory in presidential elections.
"Once again, Chinese vessels are in our exclusive economic zone uninvited."
In what appeared to be another deliberate prod, Chinese officials earlier this year bestowed new names on two underwater mountains already claimed by Palau, Whipps added.
"They're now naming some of our seamounts Chinese names. Why? Why would you do that?"
A nation of some 20,000 people, Palau is one of the few countries to recognise Taiwan's claim to statehood.
It is a stance that has angered China, which in recent years has persuaded a clutch of new Pacific friends to walk away from Taiwan in favour of Beijing.
Whipps also voiced unease about Beijing's efforts to flex its muscles in the contested channels of the South China Sea.
Chinese vessels have been involved in an escalating series of confrontations with the Philippine coast guard.
The Palauan archipelago -- a string of limestone islands and coral atolls -- lies about 800 kilometres (500 miles) east of the Philippines.
Beijing has repeatedly brushed aside an international ruling that found its claims to most of the waterway have no legal basis.
"It concerns us what is happening in the Philippines, the fights over those shoals," Whipps said.
In the four years since first coming to power, Whipps has overseen the expansion of US military interests in Palau.
This has included the ongoing construction of a long-range US radar outpost, a crucial early warning system as China ramps up military manuevers in the Taiwan Strait.
Whipps said Palau would soon dredge sections of its commercial port, making it deeper to allow more visits from US Navy ships.
"I always like to quote (former US President) Reagan. Which is: peace through strength," he said.
Palau gained independence in 1994 but allows the US military to use its territory under a longstanding "Compact of Free Association" agreement.
In return, the United States gives Palau hundreds of millions of dollars in budgetary support and assumes responsibility for its national defence.
Strong ties with Palau gives Washington "unilateral defense access across a critical swathe of the northern Pacific", said Kathryn Paik, a former adviser on US President Joe Biden's National Security Council.
Palau's economy was largely built on tourism, dominated by Chinese holidaymakers who visited in droves to see pristine beaches and world-famous dive spots.
But China effectively turned off the tap in 2017, unofficially blacklisting Palau as a destination after it refused to denounce Taiwan.
Stripped of tens of thousands of tourists each year, Whipps said he had been on a mission to build up other sectors of the economy, such as fishing and even financial services.
"We tell our friends and allies that we need you to invest. The number one investor in the past has been China," he said.
Palau was partnering with Japan, the United States and Taiwan to fill the gap, Whipps added.
"We're paying the price because of our decision to continue our very important relationship with Taiwan.
"We want to continue that friendship. And that's why it's so important for us to diversify our economy."
