The US is pushing Pakistan to bring the perpetrators of the Mumbai terror attacks to justice and to put an end to the connection between the ISI and terror groups, Secretary of State Hillary Clinton said on Wednesday as she traveled to Islamabad on a three-day visit.

The relationship between ISI and some terror groups remained a concern for the US, even though there has been a remarkable improvement in cooperation from the ISI in last nine months, Clinton told reporters travelling with her.

"... we are constantly assessing that (relationship between ISI and terrorist organisations) and because it remains a concern to us," she said in response to a question. Clinton said the US continues to raise several issues with Pakistan, with the Mumbai trial prominent among them. We are clearly pushing for the trials of the Mumbai attackers and planners to go forward," she said.

"We are very much focused on them, because we see them as a threat to Pakistan, we see them as a threat to India, we see them as a threat to stability in the region. We don't think its good for anybody," she said.

Clinton said "No" when asked: "Are you convinced that there is no more collaboration between the military and the ISI in assisting certain terrorist groups like Lashkar e-Tayyiba?" and added: "No, but I'm not unconvinced".