President Barack Obama, who met PM Narendra Modi on Tuesday, supports India's bid to enter the elite Nuclear Suppliers Group or NSG. (PTI Photo)

India will probably need to wait a while longer before it joins the elite club of nations that control trade in advanced nuclear technologies, according to three diplomats with knowledge of the process.The Nuclear Suppliers Group, or NSG, is unlikely to accept India's application for membership when it meets June 20 in Seoul because officials in New Delhi haven't yet met all the criteria for admission, said the diplomats, who represent governments inside the 48-nation group. They asked not to be named in line with diplomatic rules for discussing private deliberations.A delay could roil plans by President Barack Obama and Indian Prime Minister Narendra Modi, who were meeting in Washington on Tuesday, to bring the world's second-most-populous nation into the nuclear mainstream. It would push back a decision on Indian membership to later in the year, and risk bumping into the U.S. presidential election.Secretary of State John Kerry made a plea to member states skeptical toward India's bid for NSG membership to "agree not to block consensus on Indian admission" to the group at the Seoul meeting, accord to a two-page letter dated June 3 seen by Bloomberg News. "India has shown strong support for the objectives of the NSG and the global nuclear nonproliferation regime and is a 'like-minded' state deserving of NSG admission," Kerry wrote.A State Department spokeswoman, asked to respond to the comments from the diplomats, said that Obama affirmed that the country has met the requirements when he visited Modi in New Delhi last year.The NSG was created in response to India's 1974 atomic-bomb test that challenged the credibility of laws written to prohibit nuclear proliferation. Its network of diplomats, customs and trade officials are supposed to prevent unauthorized transfer of nuclear materials and technologies that could be used in weapons.While the diplomats said they're not opposed to letting India into the NSG eventually, they said the terms of entry require more negotiating to preserve the credibility of the trade controls. They want tighter monitoring by international nuclear inspectors as well as iron-clad assurances that Indian activities in its civilian nuclear program won't be used for military purposes.Because NSG decisions are taken by consensus, a minority of members could block India's bid to join. After months of wrangling in 2008, India won NSG trade exemptions -- without being granted full membership -- giving it access to advanced reactor technologies. Obama began the U.S. campaign to make India a member in 2010.India, North Korea and Pakistan are the only countries outside the Nuclear Non-Proliferation Treaty that have admitted to possessing nuclear weapons. Israel, which also hasn't ratified the NPT and is widely believed to possess nuclear arms, doesn't acknowledge its arsenal.The diplomats said they're concerned that admitting India before strengthening the NSG eligibility requirements would weaken the rules for other non-recognized nuclear-weapons states to join. They said India's application could be reconsidered in the fourth quarter, after the remaining proliferation concerns have been addressed. Pakistan, India's neighbor and regional rival, has also submitted an application to join the NSG, according to the envoys.Kerry signaled that India would be willing to cooperate with Pakistan's application in his letter."With respect to other possible new members of the NSG, Indian officials have stated that India would take a merit-based approach to such applications and would not be influenced by extraneous regional issues," he wrote.Modi has been lobbying for NSG membership over the last year as part of his effort to deliver reliable power the country's 1.3 billion people.© 2016 Bloomberg(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed)