VIENNA  - A controversial US-India nuclear cooperation deal ran into resistance at a key meeting here Thursday with one diplomat saying nuclear-exporting countries were unlikely to approve the deal this week. The Nuclear Suppliers Group, which controls the export and sale of nuclear technology worldwide, began a two-day meeting to debate amending its rules and allow India to share US know-how. But at the end of the first day of talks, one diplomat who attended the meeting said that agreement was "not possible" this time and an additional meeting would be necessary early in September. Asked as he came out of the meeting whether the highly-secretive 45-member NSG was likely to reach consensus by Friday (today), the diplomat, who declined to be identified, replied "it's not possible." Other delegates said nothing as they left the meeting at Japan's permanent mission to the IAEA. Bilateral discussions would be held between different NSG member states on Friday morning with a full plenary session set to begin again at around 1:00 pm (1100 GMT), diplomats said. Even though a number of countries have openly expressed reservations about the so-called 123 Agreement, which was signed by Washington and New Delhi in 2005, the head of the US delegation, State Department Undersecretary for Arms Control and International Security, John Rood, remained optimistic. "We've had a very full discussion today," he told reporters. "This is a serious subject and it's a roomful of serious people who have taken it in that manner. Certainly there are additional discussions that we will have tomorrow," Rood said. "But for our part, we continue to believe that this is a very important initiative and we remain committed to achieving an outcome that is both a net benefit for the non-proliferation regime and that meets India's energy needs." The US had "an important emerging relationship with India," Rood said. "I think there is a lot of support for this internationally. And so I remain optimistic that we're going to be able to be successful in this process," Rood said. Under NSG rules, all nuclear trade with India is banned because it refuses to sign the NPT. The United States argues that the deal will bring India closer into the NPT fold after 34 years of isolation and help combat global warming by allowing the world's largest democracy to develop low-polluting nuclear energy.