US Under Secretary of State William Burns on Thursday met Leader of Opposition L K Advani and is understood to have discussed Indo-US bilateral ties and the situation in Pakistan with him.

Burns, who is the first senior official of US President Barack Obama's administration to visit India after the recent Lok Sabha elections, spent about 45 minutes with Advani.

"Since this was the first visit of a senior USofficial after the new government took over in India, several bilateral issues and Pakistan government's lack of sincerity towards India after the Mumbai terror attacks came up for discussion," a source close to Advani told PTI.

India has already raised with the US its concern about the lack of cooperation from Pakistan in the Mumbai attacks case.

Jamaat-ud-Dawa chief Hafiz Saeed, suspected to the mastermind behind the 26/11 attack, was recently released by a Pakistan court.