"I would like to say that I believe in his sincerity because he himself is a victim of the terror attack. His wife, one of the tall leaders of the subcontinent fell victim to the senseless brutal terror attack," Mukherjee said.

"I believe he (Zardari) has desire to fight against terrorism," he told Karan Thapar's programme 'Devil's Advocate', while describing the Pakistan President as a "nice man" and a "gentleman".

At the same time, he added "my belief is not adequate. It must be backed by action taken by the government and authorities of Pakistan".

Mukherjee, who described Pakistan Prime Minister Yusuf Raza Gilani and Foreign Minister Shah Mehmood Qureshi also as gentlemen, made it clear that "it is not a question of individual personalities."

Underlining that the incumbent government of Pakistan has the "responsibility" to act, he said "When we talk, we talk of the incumbent government."

Mukherjee, however, refused to comment on the system of Pakistan, saying "it is for them to address this issue."

Pressing for tough action by Pakistan to end cross-border terrorism, the External Affairs Minister said "Onus is on Pakistani authorities to dismantle the infrastructure facilities available to the terrorists, to bring to justice the perpetrators of terror and to cooperate with India in achieving this objective."

He maintained that India's focus was at present on the issue of how terrorism is tackled by Pakistan rather than on ways to improve bilateral relations.

"Relations between India and Pakistan is not the pointed issue at this point of time. Pointed issue is how to fight terrorism. It is not the question of improving bilateral relationship. Bilateral relations are there. People to people contact is still there," he said.

Mukherjee also rejected the contention of British Foreign Secretary David Miliband that India had raised the "temperature" in ties with Pakistan.

"We have never raised the temperature. This is the phrase I think the British Foreign Secretary used and I do not think that…no I have not raised the temperature," he said.

Pointing out that India has not stopped the communication line with Pakistan, Mukherjee said "But what we want? We want that the perpetrators are brought to justice."

Mukherjee emphasised that infrastructure available to the terrorists in Pakistan should be dismantled and Pakistan authorities must fulfil this commitment.

He said it has been made clear even to the US that India's desire to see end to terrorism should not be seen in the context of Indo-Pak ties.

"The issue is not relationship between India and Pakistan. The issue is how to fight terrorism, how to dismantle infrastructure facilities available on Pakistani territory with the Pakistani elements who use these and attack India. How to bring the terrorists to justice? These are the issues. Not the India Pakistan relationship," he said.

He said there was no reason for the US not to understand this view.

He refused to comment on former Pakistan Foreign Minister Khurshid Mehmoood Kasuri's claim that India and Pakistan were close to solving Kashmir, Siachen and Sir Creek issues through back-channel talks.