The speculation of the change was sparked by remarks of Prime Minister Yousuf Raza Gilani four days after the meeting.
Gilani took the top brass in the Foreign Ministry by surprise by saying during an interaction with reporters at his home in Lahore that a "fresh team" would carry forward talks with India to resolve outstanding issues like the Kashmir.
Reporters who attended the interaction did not make much of the remarks and Gilani did not explain what he meant by the term "fresh team".
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.
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 amenable to 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.
The government ordered the review of Pakistan-US ties after a cross-border NATO air strike killed 24 Pakistani soldiers in November and the two countries have been unable to bring their relations on an even keel since then.
However, the remarks immediately triggered speculation in the Foreign Office that Khar's portfolio could be changed during an upcoming cabinet reshuffle.