WASHINGTON (AFP) - US President George W. Bush on Wednesday signed legislation to enact a landmark US-India civilian nuclear agreement, celebrating "the growing ties between the world's two largest democracies." "This agreement sends a signal to the world: Nations that follow the path to democracy and responsible behavior will find a friend in the United States of America," Bush said at a lavish White House signing ceremony. Indian External Affairs Minister Pranab Mukherjee will visit Washington Friday to Washington so that he and US Secretary of State Condoleezza Rice can formally sign the accord itself, the US State Department announced. Bush and Indian Prime Minister Manmohan Singh signed the deal in July 2005, touching off a difficult battle with wary lawmakers on either side and critics who warn it undermines global efforts to curb the spread of nuclear know-how. Evidently savoring the resulting diplomatic victory in the twilight of his term, the US president welcomed "the honor of signing legislation that builds on the growing ties between the world's two largest democracies." The agreement offers India access to sophisticated US technology and cheap atomic energy in return for allowing UN inspections of some of its civilian nuclear facilities " but not military nuclear sites. Washington imposed a ban on US-Indian civilian nuclear trade after India's first nuclear test in 1974, but US officials have said a new approach is needed to help the world's largest democracy meet its booming energy needs at a time of skyrocketing oil prices and global warming fears. US lawmakers attached safeguards on preventing the spread of nuclear weapons technology before passing it overwhelmingly last week and handing the increasingly unpopular Bush administration a foreign policy victory. But critics say it still undermines global efforts to curb the spread of nuclear weapons, because India has refused to sign the international non-proliferation treaty (NPT). Bush said the accord meant India would be able to satisfy its booming economy's thirst for energy while curbing its dependence on fossil fuels linked to climate change, while the United States would gain access to India's lucrative nuclear market. "The American people are proud of our strong relationship with India. And I am confident that the friendship between our two nations will grow even closer in the years ahead," he said. Vice President Dick Cheney, US Secretary of State Condoleezza Rice, Energy Secretary Samuel Bodman, key US lawmakers who backed the agreement, and India's ambassador to Washington, Ronen Sen, attended the ceremony. Neither Democratic White House hopeful Barack Obama nor Republican rival John McCain were invited "because of their busy campaign schedules," White House spokesman Carlton Carroll said in a statement. Bush acknowledged that US relations with India, which steered an independent course from Washington during the Cold War-era, had been "strained" but said both countries were now "natural partners as we head into the 21st century." Rice and others had to lobby hard to win approval for the deal from the International Atomic Energy Agency (IAEA), the UN nuclear watchdog, and the Nuclear Suppliers Group (NSG), which controls global atomic trade. She also pushed hard for the agreement to be approved by both Houses of Congress. Singh also had a rough ride over the deal at home: The main opposition Hindu nationalists and the Communists have both slammed it as curbing India's military options and bringing the country's foreign policy too much under US influence.