Kabul, Afghanistan ? U.S. Sen. John Kerry warned Sunday that already shaky U.S.-Pakistani relations have reached a critical juncture as calls grow in the United States to cut some of the billions of dollars in aid to Islamabad following al-Qaida leader Osama bin Laden’s killing.

Kerry, who spoke in Afghanistan before traveling to Pakistan, said sober and serious discussion was needed to resolve the widening rift amid growing suspicion that Pakistan’s security forces were complicit in harboring the al-Qaida leader, who was killed May 2 in a raid by U.S. Navy SEALs not far from Islamabad.

For its part, Pakistan is angry that it was not told about the raid in Abbottabad until after it was completed. That prompted accusations that its sovereignty had been violated.

Kerry — chairman of the influential Senate Foreign Relations Committee and the most senior American official to travel to Pakistan since the raid occurred — sounded a hopeful tone.

“I think for the moment we want to be hopeful and optimistic that we can work our way through this, get over this hiccup, and find a positive path forward,” he said.

But he made clear that patience was running thin in Washington after it was discovered that the terror leader had been living for years in a compound in a military garrison town that includes Pakistan’s equivalent of West Point.

“I think the important thing here is not to get into a recriminatory finger pointing, accusatory back and forth. The important thing is to understand that major, significant events have taken place in last days that have a profound impact on what we have called the war on terror, a profound impact on our relationship as a result,” Kerry told reporters in the Afghan capital.

He added that “we need to find a way to march forward if it is possible. If it is not possible, there are a set of downside consequences that can be profound.” He did not elaborate.

There are growing calls in the U.S. House and Senate to cut billions of dollars in aid to Pakistan.

“It is no secret that there are members of Congress who have made a call for a change in the aid program,” Kerry said.

Kerry, a Democrat from Massachusetts, was making one of the most significant visits to Pakistan by an American official in years.

In an indication of the seriousness of the visit, Pakistani President Asif Ali Zardari, Prime Minister Pakistani Prime Minister Yousuf Raza Gilani and army chief Gen. Ashfaq Parvez Kayani met ahead of Kerry’s arrival later Sunday.