Pakistani President Asaf Ali Zardari is in United States where he is expected to meet President Obama at the White House today. A media report in Washington says American concern over growing Islamic militancy in Pakistan has intensified following the assassination of the liberal Pakistani politician Salman Taseer. President Zardari is to attend the memorial service in Washington for Richard Holbrooke, President Obama's Special Representative for Afghanistan and Pakistan who died in December at the age of 69.