WASHINGTON: A US envoy on a mission to discuss post-war Afghanistan will head on a previously unscheduled trip to New Delhi after India's rival Pakistan refused his visit, officials said on Wednesday.

US officials said Pakistan informed them that it did not want to receive special envoy Marc Grossman until Islamabad completes an ongoing review of relations with Washington, which have sunk to rock-bottom in recent months.

The State Department said Grossman would head on Friday to India, whose support for Afghanistan and President Hamid Karzai is deeply resented by many Pakistanis who accuse New Delhi of trying to use the issue against Islamabad.

State Department spokeswoman Victoria Nuland said that the United States was not trying to send any message to Pakistan through Grossman's trip to India and reiterated that he would have liked to visit.

“We made clear that we would welcome a stop by Ambassador Grossman in Islamabad on this trip,” she told reporters.

“The Pakistanis are looking hard internally at our relationship. They asked us to give them time to do that, so he will not be going there on this trip,” she said.

Nuland said that the United States welcomed efforts by India, which has given more than $2 billion in aid to Afghanistan and plans to take a larger role training Afghan troops and security forces.

“We believe that India has a role to play in supporting a democratic, prosperous future for Afghanistan,” she said.

Pakistan has launched a review of its relations with Washington amid a drastic deterioration of ties, particularly after US forces killed Osama bin Laden during a unilateral raid in the garrison town of Abbottabad last year.

Islamabad has demanded an apology and curbed cooperation after a Nato air strike near the Afghan border on November 26 killed 24 Pakistani troops.

President Barack Obama has voiced regret but stopped short of a full apology.

US Secretary of State Hillary Clinton said last week that Grossman would seek to advance reconciliation in Afghanistan and talk to President Karzai about a resumption of preliminary talks with the Taliban.

The United States wants to withdraw most forces from Afghanistan in 2014, ending more than a decade of war.

But many US officials have deep concerns about the role of Pakistan, believing its intelligence services maintain ties with Islamic extremists inside Afghanistan.

After New Delhi, Grossman heads to Afghanistan on Saturday for talks with Karzai.

He is also visiting Qatar, Saudi Arabia, Turkey and the United Arab Emirates on his nearly two-week trip.