US Defense Secretary Chuck Hagel's first trip to Afghanistan was overshadowed on Sunday by a contentious speech by President Hamid Karzai and a security scare that forced their press conference to be cancelled.
Karzai and Hagel's appearance in front of the cameras was to be a key part of the Pentagon chief's visit to Afghanistan as strained US-Afghan ties focus on the withdrawal of NATO-led foreign troops by the end of 2014.
But the event was scrapped just a few hours before it was due to be held at the presidential palace in Kabul, with US officials citing unspecified security concerns.
Hagel's trip was also marked by two deadly suicide bombs on Saturday -- one within his earshot in Kabul -- and further delays to the planned transfer of the controversial Bagram jail from US to Afghan control.
In a provocative speech on Sunday, Karzai said the US was in daily talks with the Taliban and that insurgent suicide attacks enabled the international military force to justify its presence in Afghanistan.
"The bombs that were detonated in Kabul and Khost were not a show of force, they were serving America," he said in the televised speech, referring to the two suicide blasts in which 19 people were killed.
"It is their slogan for 2014, scaring us that if the US is not here our people will be eliminated," he said, without giving further details.
General Joseph Dunford, commander of the NATO forces in Afghanistan, strongly criticised Karzai's speech and was forced to deny that the US and Taliban were working together.
"President Karzai has never said to me that the United States was colluding with the Taliban," Dunford told reporters.
"It's categorically false, we have no reason to collude with the Taliban, we have no reason to be supporting instability in Afghanistan.
"I don't know why President Karzai might be doing this," he added. "I guess his perspective is maybe it's productive to air these differences in public... but I let others judge if that's being particularly helpful."
Hagel's spokesman denied that the press conference was scrapped due to the speech, saying it was a decision "made in consultation with our Afghan partners".
Hagel and Karzai's meeting, which went ahead as planned on Sunday, came as the two countries face up to a testing transition phase in which NATO-led troops exit Afghanistan and Afghan forces take on fighting the Taliban alone.
The US and Afghanistan are also negotiating a strategic pact that will determine the US presence in Afghanistan after the end of the international combat mission.
Karzai raised another point of friction on Sunday by issuing a decree banning international forces from entering university grounds after alleged harassment of students.
Also troubling US-Afghan ties has been a long dispute over the fate of suspected militants held by the US at Bagram jail.
A final hand-over scheduled on Saturday was delayed due to last-minute disagreements, officials for both sides said.
"There's probably a slight difference of perspective between us and the Afghans and we're working out that right now," Dunford admitted.
"Transitions are tough," he said. "Our relationship is changing, it's maturing, we're moving into support as they move into the lead and we're going to have to grind through issues as they occur."
"All these issues that are going on right now, this is part of transition."
He denied the allegations of NATO harassment of students and declined to say when US special forces would leave Wardak province despite a deadline set by Karzai two weeks ago that expired on Sunday.