NEW DELHI - An ex-United Nations diplomat and a veteran politician emerged on Friday as contenders to lead India's main opposition Congress party as it prepares to elect a new president from outside the Nehru-Gandhi dynasty for the first time in nearly 25 years.

Shashi Tharoor, a three-term federal lawmaker who previously served as a U.N. Under-Secretary General, said he had submitted nomination papers to lead the 137-year-old party.

The Congress, which helped lead India's struggle for independence from Britain that was achieved in 1947 and dominated Indian politics for decades afterwards, has mostly been led by a member of the Gandhi family.

Sonia Gandhi is currently the party's interim president after her son, Rahul, resigned from the position in July 2019.

The party has seen its fortunes slide, losing two successive general elections since 2014 at the hands of Prime Minister Narendra Modi's Bharatiya Janata Party (BJP), which has also wrested control of some states from the Congress.

The BJP has long advocated a hard right nationalist posture and an end to what it is says is appeasement of minority groups in a pre-dominantly Hindu India. The Congress has typically promoted a secular polity.

Tharoor's candidacy will be challenged by veteran Congressman Mallikarjun Kharge, currently the leader of the opposition in India's upper house of parliament, who is also seen as a Gandhi family loyalist.

A former state lawmaker from eastern Jharkhand state has also filed nomination papers.

Madhusudan Mistry, the Congress official in charge of running the party election, said the Gandhis would remain neutral. "The Gandhi family has not endorsed anybody's nomination," Mistry told reporters.

Around 9,000 party delegates across the country will vote for a new Congress president on Oct. 17, with results likely to be declared two days later.

(Reporting by Devjyot Ghoshal, Editing by Mark Heinrich)