The Union of Comoros, an archipelago in the western Indian Ocean, became the 20 member of the regional grouping yesterday.
By inducting the US as a dialogue partner, IOR-ARC is looking to counter the threat from China that has been increasingly assertive of late in both the Asia-Pacific region and the Indian Ocean.
"These kinds of regional and multilateral institutions play a vital role in addressing the shared challenges that we have and building a more prosperous and peaceful region. As you know, that part of the world is extremely strategically important," State Department spokesperson Victoria Nuland told newspersons in Washington.
"We are glad to see the States around the Indian Ocean working together. And we welcome the opportunity to be part of that conversation in a dialogue capacity," she said.
To a specific query about Iran that had opposed the inclusion of the US in IOR-ARC, Nuland noted, "I think it speaks to the fact that other States in the region very much welcome having us as a dialogue partner."
(with PTI inputs)