The nine-day laborious WTO talks to salvage the Doha trade round collapsed on Tuesday after the United States was locked in a deadlock with India and China over import rules for farm products.

WTO Chief Pascal Lamy said the core group of seven nations, including India, US, EU, China and Brazil, failed to reach a convergence over Special Safeguard Mechanism sought by developing countries against agriculture imports.

The seven-year old trade talks, launched in 2001, got bogged down this time around as India and China demanded lower trigger point for imposing higher duties in case of import surge, sources said.