John Kirby
US Secretary of State John Kerry (R) speaks to US State Department spokesperson John Kirby.Reuters

With Indian intelligence reports holding terrorist groups in Pakistan responsible for the Pathankot airbase attack, over 20 US lawmakers have come forward to support India, said reports.

The United States has reportedly warned the Nawaz Sharif government in Pakistan against the absence of concrete action against the perpetrators, saying it expects a "thorough, complete, fair and transparent" probe into the attack.

"We certainly look forward to and expect a thorough, complete, fair and transparent investigative process. We are going to have to let it work through," PTI quoted US State Department spokesperson John Kirby as saying.

"They (Pakistan) said they're going to investigate it. They said they're not going to discriminate between terrorist groups when they conduct counter-terrorism operations," he added.

Kirby said the US wants the probe to be discussed transparently when complete, and is looking forward to see the results of the investigation soon.

Coming out in support of India, several senior US government officials from both the Republican and Democratic parties have indicated a right course of action from Islamabad would help improve its ties with New Delhi.

The US State Department also warned Pakistan against protecting the terrorists, saying it would make it difficult for the Obama administration to convince the Congress to approve any new military aid for the country.