How does a president negotiate with his six most important alliance partners at a meeting across the ocean while dealing with an opposition at home that balks at a budget he deems essential for America’s standing at home and abroad?

That’s the question that President Biden faces as he takes off Wednesday for hard-and-fast talking at Hiroshima, where the Americans dropped the first atomic bomb in warfare on August 6, 1945, three days before the A-bombing of Nagasaki, prompting Japan’s surrender on August 15.

Mr. Biden will, of course, “pay his respects to the lives of the innocents who were killed,” said the White House National Security spokesman, John Kirby, avoiding a straight answer to whether he would “apologize” for the bombing — also overlooking the question of whether all those who perished at Hiroshima, a military center for Imperial Japan, were all that innocent.

The real challenge, Mr. Kirby made clear, will be to buttress cooperation among America’s G-7 allies, including the host, Prime Minister Fumio Kishida of Japan, and the leaders of the United Kingdom, France, Germany, Italy, and Canada.

Mr. Kirby exuded confidence in Mr. Biden’s ability to focus on the topics before the G-7 — defense, climate change, economics, and the supply chain — without getting too distracted by the great budget and debt debate in Washington.

“The president can travel overseas and evaluate our defense,” Mr. Kirby told White House reporters, “and also work with congressional leadership.”

That Mr. Biden insists on joining the G-7 meeting, rather than, say, sending Vice President Harris obviously shows the urgency of the G-7 rallying around Ukraine against the Russians while also curbing Communist Chinese aggression in Asia.

Mr. Biden’s decision to break away from the bitter negotiations with congressional leaders at Washington to see the leaders of America’ allies shows the priority placed on both Ukraine and such hot spots as North Korea, the Republic of China on Taiwan, and the South China Sea.

Mr. Biden did make a concession to the debt ceiling turmoil by announcing he would return home to fight the battle of the budget rather than go on after the G-7 to Australia and Papua New Guinea. Those stops had been seen to be critical for America’s stand against Chinese expansionism in the southern Pacific.

“Absolutely the PRC will be on the agenda,” said Mr. Kirby, using the initials for Communist China’s formal name, the People’s Republic of China. All G-7 nations, he said, “are of a common mind about how to deal with the PRC.”

For sure, Mr. Kirby added, “economics will be a part of that discussion” along with security of the region encompassing Taiwan and  the South China Sea. There would, though, be no avoiding the impasse over the budget.

“There are countries like Russia and China that would like nothing better than to see the U.S. default” on debt payments, Mr. Kirby argued.

Mr Biden’s decision to take off for Japan and the G-7 reflects intensification of defense ties with America’s two northeast Asian allies, Japan and South Korea. Japan’s foreign ministry left no doubt of the consuming importance of Mr. Biden’s mission to Hiroshima, where he’s expected to sit down with Mr. Kishida before the G-7 convene.

“The international community is at an historic inflection point,” said the ministry, citing “Russia’s aggression against Ukraine.” Japan, with an eye on Chinese claims to Taiwan and North Korea’s nukes and missiles, would “work closely with the U.S. to firmly reject any attempt to unilaterally change the status quo by force.”

Several other national leaders will attend the G-7 as observers. South Korea’s president, Yoon Suk-yeol, whom Mr. Biden hosted last month in Washington, will confer again with Mr. Biden and will also meet with Mr. Kishida in a show of “trilateral” cooperation after years of acrimony over a wide range of issues dating from Japanese colonial rule.

Mr Biden, though, will have to look over his shoulder at the debate back home. “We wouldn’t be having this discussion about the effect of the debt ceiling,” Mr. Kirby said plaintively, if Congress “did its job.” Congress, no doubt, would say the converse.

Mr. Biden was sure, though, that America’s allies would appreciate the problem. As leaders of democracies, he maintained, they  “understand and respect America’s leadership on the world stage.”