ISLAMABAD (Reuters) - Afghanistan would support Pakistan in case of military conflict between Pakistan and the United States, Afghan President Hamid Karzai said in an interview to a private Pakistani TV channel broadcast on Saturday.

The remarks were in sharp contrast to recent tension between the two neighbors over cross-border raids, and Afghan accusations that Pakistan was involved in killing the chief Afghan peace envoy, former Afghan president Burhanuddin Rabbani, by a suicide bomber on September 20.

"God forbid, If ever there is a war between Pakistan and America, Afghanistan will side with Pakistan," he said in the interview to Geo television.

"If Pakistan is attacked and if the people of Pakistan needs Afghanistan's help, Afghanistan will be there with you."

Such a situation is extremely unlikely, however. Despite months of tension and tough talk between Washington and Islamabad, the two allies appear to be working to ease tension.

In a two-day visit to Islamabad, U.S. Secretary of State Hillary Clinton issued stern warnings and asked for more cooperation in winding down the war in Afghanistan, but ruled out "boots on the ground" in North Waziristan, where Washington has been pushing Pakistan to tackle the Haqqani network.

The Haqqani are a group of militants Washington has blamed for a series of attacks in Afghanistan, using sanctuaries in the Pakistani tribal region along the Afghan border.

Pakistan is seen as a critical to the U.S. drive to end the conflict in Afghanistan.

Pressure on Islamabad has been mounting since U.S. special forces found and killed Osama bin Laden in May in a Pakistani garrison town, where he apparently had been living for years.

The secret bin Laden raid was the biggest blow to U.S.-Pakistan relations since Islamabad joined the U.S. "war on terror" after the September 11, 2001, attacks on the United States.

Karzai said tensions between the United States and Pakistan did not have any impact in his country's attitude toward Pakistan.

The TV channel, Geo, did not say when the interview was conducted.

Afghans have long been suspicious of Pakistan's intentions in their country and question its promise to help bring peace. Karzai repeated that concern in his remarks.

"Please brother, stop using all methods that hurt us and that are now hurting you.

"Let's engage from a different platform, a platform in which the two brothers only progress toward a better future in peace and harmony," he said.

Following the death of Rabbani, Karzai said he would cease attempting to reach out to the Afghan Taliban and instead negotiate directly with Pakistan, saying its military and intelligence services could influence the militants to make peace.

(Reporting by Augustine Anthony; Editing by Chris Allbritton and Michael Roddy)