Former Indian Prime Minister Manmohan Singh, known for his landmark economic reforms and a historic nuclear agreement with the U.S., has passed away at the age of 92. Singh was admitted to New Delhi’s All India Institute of Medical Sciences after collapsing at home, but despite medical efforts, he was declared dead late Thursday.

Singh, a mild-mannered technocrat and one of India’s longest-serving prime ministers, led the country from 2004 to 2014. A respected economist, he was instrumental in opening India’s economy in 1991 as finance minister, steering the country away from a socialist framework toward market-driven reforms. Singh also signed the 2008 U.S.-India nuclear deal, ending decades of nuclear isolation.

While widely admired for his integrity, Singh’s tenure was marred by corruption scandals involving his ministers, particularly during his second term. These controversies contributed to the Congress Party’s defeat in the 2014 elections to Narendra Modi’s Bharatiya Janata Party. Despite this, Singh’s legacy includes significant milestones like the Right to Information Act and rural employment guarantees.

Prime Minister Narendra Modi and opposition leader Rahul Gandhi paid tribute to Singh’s contributions. Modi called him “one of India’s most distinguished leaders,” while Gandhi lauded his economic acumen and leadership. U.S. Secretary of State Antony Blinken highlighted Singh’s role in strengthening U.S.-India relations.

Born in pre-partition Punjab, Singh earned a doctorate from Oxford University and held key economic roles before entering politics. He served as finance minister during India’s 1991 economic crisis, implementing reforms that shaped the nation’s modern economic trajectory. Singh’s leadership also saw efforts to resolve disputes with Pakistan and China, though challenges like the 2008 Mumbai attacks hindered progress.

Singh is survived by his wife, Gursharan Kaur, and three daughters.