Washington says, it has evidence linking the Pakistan government to the Haqqani network that attacked US Embassy in Kabul this week. US Ambassador to Pakistan Cameron Munter said in Islamabad that this must stop. He said the two sides should make sure that they work together to fight terrorism.Earlier, a senior US defence official said in Washinton that US suspects that Pakistan's spy agency ISI could be behind the attack on its Embassy in Kabul this week. Unamed official quoted by Wall Street Journal they are looking for direct evidence in this regard. The blast left 27 people dead.The remarks come close on the heels of a warning from Defense Secretary Leon Panetta that the US would retaliate against attacks on its forces in Afghanistan by Pakistan-based militants. US Vice President Joe Biden too has criticised Pakistan in recent days as an unreliable ally in the war against terrorism.