NEW YORK, Jan 29: Terrorists could steal some of the vast stocks of unsecured radioactive material in Pakistan and India to launch a "dirty bomb" attack that could scuttle peace moves between the two countries , a US Senate committee in Washington was told on Wednesday.

"The first act of nuclear terrorism will be a momentously bad event," analyst Michael Krepon of Smitten institute told the Senate Foreign Relations committee during hearings on "Pakistan, India: Steps towards Rapprochement".

"In tense regions like South Asia, the detonation of a 'dirty bomb' could scuttle a peace process and generate severe pressures for escalation," he said. US officials have warned they are concerned that terrorists could use "dirty bombs", conventional explosives packed with radioactive material.