India says it has good, but not conclusive, evidence that Pakistan's spy agency was involved in a series of bombings that killed 186 people in Mumbai in July.
Indian National Security Advisor M.K. Narayanan told the CNN-IBN television network Sunday the government does not have what he called "clinching" evidence.
The security official said the evidence would be presented to Pakistan when the foreign secretaries of India and Pakistan meet next month.
Indian police last month blamed Pakistan's Inter-Services Intelligence and the Lashkar-e-Taiba militant group for the seven bombs that ripped through commuter trains and platforms in Mumbai.
Both Pakistan and the Lashkar militant group quickly denied any involvement in the attacks.
Pakistan said if India could provide credible evidence to prove the charge, Islamabad would deal with the those involved.