The US has asked Pakistan to stop using insurgent groups like LeT for achieving its policy goals, warning that America may be impelled to use "any means" at its disposal if Islamabad failed to deliver in the war against terror.The message, was conveyed in a letter from US President Barack Obama to his Pakistani counterpart Asif AliZardari.It also includes an offer to try to reduce tensions between India and Pakistan. A leading US daily reports that the two-page letter, hand-delivered by National Security Adviser General (retd) James Jones during his visit to Islamabad early this month, offers Pakistan enhancement of strategic partnership if they act as wished by the US, besides additional military and economic aid. Jones had also told News Agency that the US was "doing everything" to make sure that Pakistan smashes terror groups like Lashkar-e-Toiba and denies them safe havens.