KABUL, afghanistan Staff Sergeant Stephen Christopher Whitfield readied his sidearm for firing - "chambering a round," the troops call it - as we stepped outside Combat Outpost Little Blue, north of Kandahar.
Does it concern him, having his base right next to another base manned by armed Afghan forces?
"Of course it does, with the insider threats that are taking place in the last couple of months," he told me, "but you deal with whatever situation you have, and we've never had a problem out here."
That's true. There have been no insider attacks here in Shah Wali Kot. But elsewhere in Afghanistan they've left at least 52 U.S. military personnel dead since the war began.
"Mutual trust and respect," explains Sgt. Whitfield. "I guess if you treat people right, things won't happen, but it's still a concern because of the attacks that have taken place."
But that mutual trust has been damaged here by the attacks elsewhere. And that's probably the case wherever U.S. troops are working closely beside their Afghan partners.
New security measures, meant to ensure the safety of U.S. troops, are actually driving a wedge between them and the Afghan forces they fight beside. Their motto, "shoulder to shoulder," is starting to look more like "at an arm's reach."
Now, whenever U.S. soldiers take the few short steps to the Afghan side, not only are they all armed, but they go in greater numbers, insist that all the Afghans are unarmed, aside from the two senior Afghan officers (for their own personal safety), and that there's always a U.S. Guardian Angel assigned to keep watch over everything.
Unlike the other soldiers, the Guardian Angel's weapon is primed and ready for firing - a chamber in the round. His sole job is to identify and neutralize any threat.}
Inside the outpost, U.S. soldiers are required to carry a weapon at all times. No armed Afghans are allowed on the base.
From an Afghan perspective, that stand-offish, tooled-up approach can give the impression that the relationship built on mutual trust may not be that mutual after all.
District Police of Chief Bacha Khan takes pride in his men's discipline and integrity, and his record of zero insider attacks. But he admitted the new measures carry the danger of sending the wrong message.
"This is not good news," he said. "On the one hand, we have to fight together on the battlefield, but on the other hand, we cannot go to the Americans with guns. There has to be an end to this."
Two weeks ago, there was a very abrupt end to a joint operation to clear an area of Taliban fighters when the order came down for the soldiers of Task Force Lancer to immediately cease their activity and return to the base.
That left the stunned Afghan forces to finish the operation on their own.
Lt. Col. Leroy Barker said the Afghan security forces were surprised, but understood the reasoning behind the order to bring an immediate halt to all joint operations.
I asked him if, through those actions, Afghans were getting the sense that maybe U.S. troops didn't trust Afghans - not just in general, but right here in Shah Wali Kot.
"Yes, that may be the message they're getting, and we tried to soften that blow as much as we could," said Barker. "We threw up a lot of these barriers, but I think our interaction, which is the key piece to this, is making sure they understood what we were trying to do."
That's not to say the U.S. soldiers don't venture out from their bases. They took us to a crucial checkpoint, now manned by armed Afghans. The Americans were armed, too, and more than one Guardian Angel stood guard.
They've put a hold on joint operations until all Afghan forces in the district are vetted. They're taking fingerprint scans, iris scans and photographs to build a national database. They hope to finish the process this week.
Then they'll be back to partnering, side by side with armed Afghans. The men and women from Task Force Lancer make up what the Pentagon calls Security Force Assistance Teams, or SFAT. Top U.S. commanders, from Gen. John Allen on down, call SFATs the "game changer" - a vital component to making sure U.S. troops can hand over security duties and withdraw from Afghanistan by the end of 2014.
No partnering, no mission.
Lt. Col. Barker said he's confident the Afghan forces will get right back to the battlefield and not harbor any resentment toward his troops.
"They felt guilty about the insider attacks themselves," he said, "so they understood, they were supportive, we're going to continue this relationship the best we can, and they're good with it."
Both sides have to be good with it. It's a matter of trust.