The US delegation led by Deputy Secretary of State Thomas Nides was taken by surprise when Khar publicly contradicted the President during a meeting held at the Governor's House in Lahore on April 4, diplomatic sources told PTI. 

Zardari was then camping in the capital of Punjab province to interact with workers of his Pakistan People's Party. Nides raised the crucial issue of Pakistan's participation in a conference on Afghanistan to be held at Chicago in May, and Zardari said his government was amenableto discussing the matter if Washington extended a formal invitation, the sources said.

At this point, Khar intervened and said the issue could not be taken up till a joint session of parliament completed an ongoing review of Pakistan-US relations, the sources said. Any discussion on the Chicago conference could be held only after the review, she was quoted as saying.  The sources said the US delegation was surprised by the "argumentative" tone adopted by Khar in the presence of the President, who is perceived as the PPP's main  decision-maker on crucial foreign policy issues.