Flush from its upset victory in national elections, India's Congress Party chose Sonia Gandhi as its new parliamentary leader Saturday, a move that virtually ensures her selection as prime minister if she chooses to accept the post.

At a jubilant ceremony in Parliament's central hall, newly elected Congress Party lawmakers unanimously elected Gandhi, the Italian-born widow of prime minister Rajiv Gandhi, then lined up to present her with roses when she arrived at the Parliament building a few minutes after the vote.

On Thursday, results from national elections that were spread over three weeks gave Congress and its allies a dramatic and unexpected victory over the governing coalition led by Prime Minister Atal Bihari Vajpayee and his Hindu nationalist Bharatiya Janata Party (BJP).

Because Congress and its partners fell short of a majority in the 545-seat Lok Sabha, or lower house, they will have to form a government in alliance with other parties -- including India's two main Communist parties -- after which the new ruling coalition will choose the next prime minister.

That step, however, is considered little more than a formality because leaders of the main parties that could form a coalition have already signaled their support for Gandhi, although they have yet to decide whether to join the new government or support it from outside.

There has been speculation that Gandhi might forgo the prime minister's job to spare the party from attacks based on her foreign origin, which some analysts have suggested could compromise her effectiveness as a national leader. Gandhi has remained noncommittal in public. At a news conference after the Congress victory Thursday, however, she noted that whoever is chosen as parliamentary leader has customarily served as prime minister.

There was nothing in her demeanor Saturday to suggest that Gandhi, having led her party back to power after eight years in the political wilderness, would shrink from the chance to lead the world's second-most populous country.

"I feel deeply humbled. I feel greatly privileged," Gandhi, 57, told the Congress lawmakers after the vote. "The people of India have spoken. They have once again reaffirmed what we all believed within our hearts. They have asserted that the soul of our nation is inclusive, secular and united."

Dressed in a cream-colored sari, Gandhi also made reference to the famous political dynasty whose leadership she assumed after being drafted into politics in 1998, seven years after her husband was killed by a suicide bomber.

"I stand here today, in the space once occupied by my greatest teachers," she said. "Their lives have guided me throughout my journey." In addition to her late husband, she was referring to her mother-in-law, Indira Gandhi, the prime minister who was assassinated by her bodyguards in 1984; and Jawaharlal Nehru, Indira's father and the country's first prime minister, from 1947 to 1964.

The prospect of a government in which communists could have a significant voice has rattled financial markets, which prospered under the defeated coalition. Investors have expressed concern that the new coalition could slow or even reverse economic reforms, including the privatization of state-run industries, which began under a Congress government in 1991 but gathered steam under Vajpayee.

One key stock index suffered its biggest one-day drop in more than three years Friday, the same day a leader of the Communist Party of India-Marxist (CPI-M) called for the dismantling of the privatization ministry.

Congress Party leader Manmohan Singh, a former finance minister, tried to reassure investors, telling reporters that "we are not against disinvestments per se, if it is shown to be in the national interest. We are open to all options."

The scope and pace of economic reforms will be a key issue as Congress seeks to persuade uncommitted leftist parties to join the governing coalition. But most of the parties have already pledged their support to Gandhi as prime minister, regardless of whether they formally join the government.

"All will have to accept the Congress leader in a coalition government," CPI-M spokesman Sitaram Yechury told the Press Trust of India news service.

The main voice of dissent was that of the BJP. "It is unfortunate that the Congress Party could not find as its leader a person of Indian origin from among a population of" a billion people, Mukhtar Abbas Naqvi, the party spokesman and general secretary, said in a statement. "Our best wishes are with the new government, but we will keep a close watch on all issues of national importance."

Special correspondent Rama Lakshmi contributed to this report.

Newly elected Congress Party lawmakers present Sonia Gandhi with a garland after her election as the party's leader and probable prime minister.