Headley's case involves a trial in the US and Pakistan has not been given access to him, Foreign Office spokesperson Tehmina Janjua told a weekly news briefing.
She was responding to a question about Headley's testimony linking Pakistan's ISI to the Mumbai attacks.
Pakistan is "not in a position to determine the details of what he (Headley) is saying or what he is not saying", Janjua said.
"Therefore, what we can say is that it is our expectation that all sides will refrain from vitiating the atmosphere by baseless speculation" from the trial, she said.
Headley's testimony in a Chicago court, which is conducting the trial of his friend Rana, has detailed the alleged role of some ISI officers and Lashker-e-Taiba commanders in planning and executing the Mumbai attacks.
The son of a Pakistani broadcaster and an American woman, Headley struck a plea bargain with US authorities to testify against other suspects in order to avoid the death penalty.
In response to another question, Janjua said Pakistan had given India a non-paper on the Siachen issue during a recent meeting of the Defence Secretaries of the two countries in New Delhi.