India and Oman have annual trade of less than $13 billion, but the relationship is important for New Delhi as the Gulf nation is a gateway to the narrow Strait of Hormuz between Oman and Iran
Brazil, Russia, India, China and South Africa - a group of major emerging economies known as BRICS - launched the bank in 2015 and started formal talks with potential new members last year.
“New members will have in NDB a platform to foster their cooperation in infrastructure and sustainable development,” said NDB President Marcos Troyjo in a statement.
“We will continue to expand the bank’s membership in a gradual and balanced manner,” he said.
Since launch, the Shanghai-headquartered lender has signed off some 80 projects worth $30 billion in all of its five member countries stretching across sectors from transport, water and sanitation to clean energy or digital and social infrastructure.