Negotiations between top US and Indian officials reached their fourth day on Friday as the two sides struggle to come to terms on how to implement a deal allowing the United States to assist India in the development of civilian nuclear energy, according to dpa. US State Department deputy spokesman Tom Casey said the talks, originally scheduled to last for a couple of days, have been extended because the United States and India are committed to reaching an agreement. "It's clear that both countries have the good will necessary to do this, are willing to work with one anther to achieve an agreement," Casey said, "and we're certainly hopeful that we'll get one in the very near future." US President George W Bush and Indian Prime Minister Manmohan Singh signed the deal in 2006, opening the door for the US to share technology and nuclear fuel with India after months of difficult negotiations. But the two countries have been unable to come to terms on how to move forward, with the United States balking at India's demand that it be allowed to reprocess nuclear fuel supplied by the United States. US law prohibits the reprocessing of supplied fuel because the practice could aid a nuclear weapons programme. To try to bridge differences, India sent a high-level delegation to the United States, including national security advisor, MK Narayanan, Foreign Minister Shivshankar Menon and the head of the country's Atomic Energy Commission, Anil Kakodar. They are meeting with US Undersecretary of State Nicholas Burns, who oversaw US-led negotiations to complete the deal. The nuclear cooperation pact between the United States and India has become the cornerstone of closer relations after decades of Cold War tension. The United States slapped sanctions on India in 1998 after the country detonated a nuclear device for the first time in more than 20 years. The US Congress will again have to approve the deal once the final arrangements have been worked out, a prospect that could be more challenging for the Bush administration now that Democrats have taken control of the legislative body and have raised concerns because India has not signed on to the nuclear Non-Proliferation Treaty. The Indian delegation is in Washington for a series of meetings over several days, including with US Defence Secretary Robert Gates Monday and another one Wednesday with Stephen Hadley, Bush's national security adviser. The United States outlawed any nuclear trade with India after it first tested a bomb in 1974. As part of the deal with the United States, India was required to separate its civilian and military nuclear projects and open up its civilian reactors to inspections from the International Atomic Energy Agency (IAEA). India must also secure a safeguards agreement with the IAEA and get the approval of the 45-nation Nuclear Suppliers Group, which controls international trade in fissile materials for civilian energy.