"This is a historic first and at the same time a 'going forward' futuristic meeting of global superpowers, in the biggest country in the Pacific," Marape said in a statement on Sunday.
Biden's May 22 stopover in the capital Port Moresby would be the first visit by a sitting US president to the resource-rich but largely undeveloped country of 9.4 million people.
Papua New Guinea is being courted by China and by the US and its allies, as Marape seeks to boost foreign investment. Chinese President Xi Jinping visited the nation in 2018.
Washington has stepped up efforts to counter Beijing's growing influence in the region after China struck a security pact with the Solomon Islands last year. China failed to reach a wider security and trade deal with 10 Pacific island countries.
China and Australia have been major aid and infrastructure donors.
Papua New Guinea is negotiating security pacts with the United States and Australia, and Marape has been invited to visit Beijing this year.
"In the Indo-Pacific conversation, PNG and the Pacific cannot be ignored. With our combined forest and sea areas, we have the world's greatest carbon sink, and the biggest sea and air space on earth," Marape said.
The 18 countries and territories in the Pacific Islands Forum cover 30 million square km of ocean. The region's leaders say climate change is their greatest security threat, amid worsening cyclones and rising sea levels.
Modi and Biden will stop in Papua New Guinea on the way to Australia for a May 24 summit of the Quad, which also includes Japan and Australia.
Marape said he had invited Biden when they met in Washington last year, and was "very honoured that he has fulfilled his promise to me to visit our country".
