The Bush administration this week is expected to begin laying out in more detail its plans to change US and international rules so India can acquire restricted nuclear materials under a controversial deal some say undermines non-proliferation standards.
India improved its chances of having new rules approved when it voted with the United States and key European states last month to threaten Iran with referral to the UN Security Council for its nuclear activities.
But some members of the US Congress remain deeply concerned that the US-India deal, agreed in Washington on July 18, is too permissive and will advance, not stem, the spread of nuclear weapons.
There also are doubts about whether India, which has a burgeoning strategic relationship with Tehran, ultimately will vote to send Iran's case to the Security Council, where sanctions could be imposed.
Several experts and congressional sources said New Delhi has not made a commitment on that issue, which could come before the International Atomic Energy Agency board of governors next month.
US officials are expected to present ideas for international rule changes when the 44-nation Nuclear Suppliers Group, which seeks to control nuclear exports, meets in Vienna, beginning on Monday, US officials and experts said.
On Tuesday, Under-secretary of State Nicholas Burns, lead negotiator on the India nuclear deal, will speak on US-India relations to the Asia Society in New York. He later travels to New Delhi for further negotiations with Indian officials.