India's powerful communists decided Monday not to formally join Sonia Gandhi's new coalition but to instead support it from outside, as shares recorded their second-largest plunge in history. Trading was automatically halted on the Bombay exchange after the main index dived 11 percent within minutes of opening on fears the communists' influence, with more than 60 of parliament's 545 seats, could derail reforms. The Bombay index extended its losses to more than 15 percent after markets reopened, forcing officials to suspend trading again for two hours. As Gandhi prepares to form her new government by Wednesday with the support of several other parties, a senior leader of the largest communist group, the Communist Party of India, said leftists would not join the coalition. He gave no details. Supporting governments from outside -- voting with them on critical issues such as confidence votes -- is common in the world's largest democracy. Armed with letters of support from a growing number of parties, Gandhi was expected to meet the president to stake a claim to power for her Congress party and its allies. President Abdul Kalam will likely accept her claim to lead the world's second most populous nation -- the fourth member of the Nehru-Gandhi dynasty, India's equivalent of America's Kennedys to do so -- after a weekend of deal-making secured the backing of almost 300 lawmakers. FORMALITY "It is a formality. We expect her to be sworn into office on Wednesday," said a leader of the Congress party, which ousted the Hindu-nationalist Bharatiya Janata Party-led coalition from office in one of India's biggest election upsets. With market panic casting a shadow over Gandhi's new government before it even begins, Congress leaders sought to calm investors. "There is no need for panic," said Pranab Mukherjee, a senior party official and front-runner for the finance minister's job, adding the new government would be investment friendly. The rupee also weakened half a percentage point, but was shored up by the central bank. The communists have reservations about the country's free-market economic reforms that Congress initiated in 1991 and is committed to carry forward. Some communist parties are also in direct opposition to the Congress in several states. Despite the slide in financial markets, which has wiped tens of billions of dollars off the value of listed companies, most analysts see the modernizing of Asia's third-largest economy as largely unstoppable. "I expect the reform process to continue in the same direction as before although we will watch how the left parties influence the pace of reforms," Sanjeev Sanyal, senior economist at Deutsche Bank, told Reuters from Singapore. "If the government comes up with a credible economic program and with a credible economic management team then this slide is a buying opportunity. It depends on the new regime to give the market a sense of future policy direction." Italian-born Gandhi will be India's first foreign-born prime minister and follows her husband, Rajiv, mother-in-law Indira and Indira's father Jawaharlal Nehru into the top job. Rajiv and Indira were assassinated. **PHOTO CAPTION*** Indian President A.P.J. Abdul Kalam shows the indelible ink on his finger after voting in India's fourth phase of national elections in New Delhi, India, Monday, May 10, 2004. (AP)