Australian prime minister Scott Morrison warned on Monday that China’s establishment of a naval base in the Solomon Islands would constitute a “red line” for Australia’s security situation, sharply raising tensions between China and Australia as Beijing pursues growing security ties with the small island nation to Australia’s northeast.

“I share the same red line that the United States has when it comes to these issues,” Morrison told a press conference on Sunday, according to Australia’s ABC news network. “We won’t be having Chinese military naval bases in our region on our doorstep.”

Morrison’s comments came after last week’s announcement of a new security agreement between China and the Solomon Islands. The agreement provides for close cooperation between Chinese and Solomon Islands security forces, which Australia fears could allow Beijing to station military personnel on the island on a permanent basis.

Morrison added that he respected the sovereignty of the Solomon Islands to pursue its own political relations, but also argued that the security of the Oceania region was also a concern for neighboring countries such as New Zealand, Fiji, and Papua New Guinea.

“We respect the right of every Pacific country to make sovereign decisions,” the Australian foreign ministry claimed in a statement following the partnership’s announcement. “We have regularly and respectfully raised our concerns with the Solomon Islands Government and will continue to do so.”

“We would be particularly concerned by any actions that undermine the stability and security of our region,” the statement added, specifying “the establishment of a permanent presence such as a military base” as one action that would provoke greater tensions.

The United States adopted a similar line after a U.S. delegation met with the Solomon Islands’ prime minister, Manasseh Sogavare, on Friday.

“The United States respects the right of nations to make sovereign decisions in the best interests of their people,” the American readout of the meeting read. “The U.S. delegation noted there are potential regional security implications of the accord, including for the United States and its allies and partners.”

Manasseh indicated that the new deal, which allows China to send its police and military personnel to the islands, would not allow Beijing to build a formal naval base. China has largely concurred, with a spokesman for the Foreign Ministry claiming that the agreement was related to “normal law enforcement and security cooperation … in line with international law and convention, and should not be over-interpreted.”

Chinese-Australian ties, once largely cordial, have grown increasingly hostile over the past decade as China’s foreign policy has become more assertive. Australia is a member of the “Quad”—the four-nation security partnership that also includes the United States, Japan, and India—and the “AUKUS” pact alongside the United States and the United Kingdom. The two alliances have been framed by both Western and Chinese observers as a strategic bulwark against Beijing’s growing power in the Indo-Pacific region.

Trevor Filseth is a current and foreign affairs writer for the National Interest.

Image: Reuters.