Prime Minister Scott Morrison meets US President Joe Biden for first time alongside UK Prime Minister Boris Johnson

Although the one-on-one meeting had been billed beforehand, Mr. Johnson joined Scott Morrison and Mr. Biden at the closed-door affair at the seaside resort town of Carbis Bay, near Cornwall.

Asked afterward why he didn’t meet alone with Mr. Biden, Mr. Morrison said: “It was an opportunity that presented because we’re all here, and so it was mutual.”

But we were particularly keen to discuss with both parties,” he continued.

Nikki Sava, a journalist at the Australian newspaper and a former adviser to Liberal prime minister John Howard, told ABC’s Insiders program it seemed Mr. Johnson was needed as an “intermediary” between Mr. Morrison and Mr. Biden.“This seemed to me like it was Boris Johnson stepping in what seemed like it might be an awkward little meeting, given Morrison’s full-on support for (former US President Donald) Trump and negative globalism, a much smoother introduction and lead-in into what will be critical discussions,” she said.

Former Liberal opposition leader John Hewson had a different theory, suggesting Mr. Johnson was there to smooth over differences over climate change. “Our media are tying itself in knots today trying to spin Biden/Morrison meeting being replaced by a trilateral including Johnson,” he tweeted. Could it be Biden not prepared to extend Morrison the privilege given his indefensible irresponsibility and stubbornness on climate?”

Mr. Morrison said after the meeting that climate change didn’t come up.

“Oh, we’ve had those discussions before. Those weren’t the subject of our discussions this afternoon,” Mr. Morrison said after the meeting. “But they are the subject of tomorrow’s sessions at the G7 Plus. And we look forward to participating in those and setting out Australia’s position, our performance, and our achievement in reducing emissions.”

Australia has set far less ambitious climate goals than many other countries, and Mr. Biden has previously sought to pressure countries to take decisive action to slow global warming.

Unlike many other world leaders, Mr. Morrison has refused to commit to a goal of net-zero emissions by 2050, saying instead Australia will aim to reach that milestone “as soon as possible”.

Mr. Morrison said the 40-minute chat was an “important” opportunity for Australia. to strengthen bonds with “the leaders of the largest advanced economies and liberal democracies around the world.”

Though reporters were not present at the meeting and the details of the discussions were unclear, the three leaders released a joint statement afterward that hinted that China would have been one of the topics of conversation. “They discussed several issues of mutual concern, including the Indo-Pacific region,” the statement said. “They agreed that the strategic context in the Indo-Pacific was changing and that there was a strong rationale for deepening cooperation between the three governments.

“They welcomed the forthcoming visits and exercises in the Indo-Pacific by the Carrier Strike Group, led by HMS Queen Elizabeth.” Asked by a reporter how often China came up, Mr. Morrison responded: “Well, you wouldn’t expect me to go into any detail about the specific discussions.

“We had the opportunity today to discuss the Indo-Pacific situation more broadly. Australia has no greater friends than the United States and the United Kingdom. “And we’ve been working on our security issues for a long time. And so we had a good opportunity to talk about those today and look to see how we can further co-operate in the future.” Australia is not one of the Group of Seven, or G7, a political forum consisting of the UK, US, Canada, France, Germany, Italy, and Japan.