Prime Minister Manmohan Singh has conveyed to US President Barack Obama India's serious concern over terror emanating from Pakistan and its lack of will to punish the perpetrators of 26/11 attacks.
On his part, Obama said the US shares India's concerns over Lashkar-e-Taiba and other terror outfits operating from Pakistan.
Singh said New Delhi wants convincing action against those behind the Mumbai attacks.
The Prime Minister, during his 45-minute meeting with Obama, also raised the issue of Indian investigators getting direct access to Mumbai attacks plotter David Headley.
Obama said the US was working through legal processes for giving India access to Headley.
"He (Obama) was fully supportive of our request for provision of such access," Foreign Secretary Nirupama Rao told reporters.
Obama also promised to keep in mind India's concerns over the end-use of the US military supplies to Pakistan after Singh voiced apprehensions in this regard.
The US President said he favoured reduction of tensions between India and Pakistan but the Prime Minister made it clear that the "future of South Asia would be determined by the manner in which terrorism is tackled".
During the meeting at the Blair House, Singh emphasised that Pakistan needed to take "convincing action" against those responsible for Mumbai attacks, she said.
Obama said the US understood India's concerns with regard to activities of Lashkar-e Taiba and other terror groups from Pakistan and Afghanistan and that Washington was "engaging" Pakistan on these issues.
While talking about the menace of terrorism emanating from Pakistan, Singh referred to Headley, activities of LeT and its chief Hafiz Saeed and HuJI terrorist Ilyas Kashmiri, Rao said.
"Unfortunately, there is no will on part of Pakistan to punish those responsible for terrorist attacks in Mumbai," Rao quoted the Prime Minister as telling Obama.
"This is where partnership of India and the US could make the difference," Singh told Obama.