Prime Minister Syed Yousaf Raza Gilani called on President Asif Ali Zardari at Aiwan-e-Sadr Thursday and apprised him about his visit to the United States to attend the Nuclear Security Summit in Washington. The two leaders also discussed 18th Constitutional Amendment Bill 2010 and political situation in the country. The President while referring to the laying of 18th constitutional amendment Bill in the Senate said the credit goes to all political parties for showing maturity and rising above partisan politics for the larger national interest. He said the Party believed that the strength of federation was in the supremacy of the parliament and strength of the federating units.