During his three-day trip to Washington, Mathai held wide range of talks on bilateral and regional issues with top US officials including the new Secretary of State John Kerry.
Among others he met deputy secretary William Burns and under-secretary of state for energy, economic growth and environment Robert Hormats.
Soon after meeting Kerry, Mathai had a three-hour long meeting with under secretary of state for political affairs Wendy R Sherman during which they discussed a whole range of bilateral and regional issues, setting the tone for the second term of the Obama administration, which sources described as "very very substantive".
Expressing satisfaction over the progress made in his meeting, sources said it was "frank and useful exchange of views."
A US state department spokesperson, familiar with the talks, said Sherman and Mathai "enjoyed a warm and positive" meeting at the state department.
Sherman expressed the US' condolences for the Hyderabad bombings and underscored the priority America attaches to India-US counterterrorism cooperation.