The DMK, a key ally of UPA with 18 Lok Sabha members, insists that India pushes for amendments to the resolution against Sri Lanka to incorporate its demand for an international probe and time-bound action against those found guilty of war crimes in Sri Lanka.
The resolution will come up for voting at the United Nations Human Rights Commission (UNHRC) in Geneva on March 21.
"If our demands are not met, it is doubtful whether our ties with the alliance (UPA) will continue...It won't continue is sure," Karunanidhi told reporters here.
Addressing a hurriedly convened press meet here, the 88-year-old leader said irrespective of the US accepting India's amendments or not, New Delhi should move them at the UN human rights body in Geneva.
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The UN body had adopted a similar US-backed resolution last year with the support of India which asked Colombo to make rapid progress on reconciliation with the ethnic Tamils.
To a question, Karunanidhi said none from the Centre had contacted him after he had warned of his party quitting the government.
DMK, an ally of UPA since 2004, has one cabinet minister and four junior ministers in the Manmohan Singh ministry.