Prime Minister Scott Morrison promised Sunday during a heated debate before the May 21 elections that Australia would cooperate with its friends to prevent China from establishing a military facility in the Solomon Islands.

China’s growing clout in the Pacific has become a hot political issue in Australia ahead of the polls, following Beijing’s announcement last month that it had signed a security pact with the Solomons.

The China-Solomons deal has not been publicly released but a leaked draft alarmed countries in the region, particularly sections that would allow Chinese naval deployments to the Solomons — less than 2,000 kilometers (1,200 miles) from Australia.

The deal sparked fears China may set up a military base in the Pacific state, though the Solomon Islands government has insisted this is not on the cards.

Morrison, whose conservative government is trailing the opposition in the latest opinion polls, has been criticized for failing to prevent China from signing the deal in a region where Australia has traditionally had great influence.

Opposition Labor Party leader Anthony Albanese described it in the televised debate as a “massive foreign policy failure”.

The prime minister has warned that establishing a Chinese military base in the Solomons would be crossing a “red line”.

Pressed during the debate on what that red line means, Morrison said: “Australia would work with partners to ensure that that type of an outcome would be prevented.”

Morrison added, however, that it would be “unwise” to speculate about specific measures that Australia might take to prevent a military base from being established on the Solomons.

“The Solomon Islands government themselves have made it very clear to us that that is not an outcome that they are seeking or supporting either. I believe it is not in their national interest to have such a presence,” he said.

During Sunday’s testy debate, the Australian prime minister and opposition leader also sparred over the rising cost of living, how best to tackle global warming, and anti-corruption measures.

But China’s political and military sway in the Pacific region has emerged as a major foreign policy concern.

Australia’s foreign minister Marise Payne held talks with her Solomons counterpart in Brisbane on Friday night during which she repeated Australia’s “deep concern” over the China security agreement and the “lack of transparency” over its content.

But she said the Solomons’ foreign minister, Jeremiah Manele, reassured her that Australia remained the Pacific state’s “partner of choice”.

The Solomons’ prime minister, Manasseh Sogavare, has reacted angrily to criticism of the China deal, saying his country was being treated like “kindergarten students walking around with Colt 45s in our hands”.

The Solomon Islands government severed ties with Taiwan in September 2019 in favor of diplomatic relations with China, a switch that unlocked investment but stoked inter-island rivalries.

Protests against Sogavare’s administration in Honiara erupted into rioting last November, with much of the city’s Chinatown set ablaze. To assist restore calm, Australia led an international peacekeeping effort.