"The US and India are working at the highest level to provide direct access to Headley. Our government has put this as the highest priority in counter-terror cooperation," US Ambassador Timothy J Roemer told journalists here.
"We recognise the sensitivity of this issue to India and the people of India," stressed Roemer, a former member of the 9/11 commission.
"We want to ensure justice is brought to these blood-thirsty terrorist attackers, whether they kill thousands of people in New York or scores of them in Mumbai," he said.
"This is an issue we want to resolve as quickly as possible," Roemer said, adding that he has written in his blog that he is "burning the midnight oil" to make this possible.
Roemer said that he has approached the highest level in the US government, including the FBI and counter-terror officials in connection with Headley's access to India.
The envoy's statement came close in the heels of President Barack Obama's similar assurance to Prime Minister Manmohan Singh during their talks ahead of the Nuclear Security Summit in US.
Expressing confidence in Obama's assurance, Indian authorities are planning on writing a formal letter to the American authorities, seeking direct access to Headley.
Headley had confessed to his involvement in the Mumbai terror attacks.