Story highlights Negotiations between the U.S. and Afghanistan over post-2014 troop levels have deteriorated

Those who have dealt with Afghan President Karzai say it's sometimes 'like dealing with a child'

The U.S. planned to leave some residual force in place to fight insurgents and train Afghan forces

The U.S. planned to leave troops in Iraq after the war but pulled all out after talks stalled

Is President Barack Obama seriously considering pulling all U.S. troops from Afghanistan by next year or is just a sign of his frustration with Afghan President Hamid Karzai?

There's no doubt that Obama has had his fill of dealing with Karzai's on-again, off-again negotiations over how many troops would remain in the country after 2014. And there's no doubt that the relationship continues to deteriorate, CNN Chief National Correspondent John King said.

"You can talk to senior officials going back into the Bush administration, they would tell you dealing with Karzai is sometimes like dealing with a child -- he's unpredictable, he changes his mind -- so that's part of it," King said.

"So If Karzai doesn't trust his own security forces, you lay this down that we might come back to a zero option, maybe you snap him into thinking, '"I'd better get to get back to the negotiating table here,'" King said.

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The tough-love approach has become the standard negotiating tactic with Karzai, CNN Foreign Affairs Reporter Elise Labott said. "They're still hammering out a deal for the long-term U.S. numbers and they know Karzai really doesn't want to be left standing alone."

U.S. and Afghan officials had been discussing a residual force in the country post-2014 to fight insurgents and train Afghan security forces.

But the relationship between the two countries soured further last month after the United States and the Taliban planned peace talks and in response, Karzai cut off negotiations.

The Pentagon said no decision has been made and talks continue.

"We continue to work through issues," Pentagon spokesman George Little said, adding, "We believe we can work through them."

Karzai does hold a bargaining chip in that a complete pullout would put the United States at a strategic disadvantage in a volatile region.

"Think about the past decade, look at a map: it's inconceivable to think there wouldn't be some kind of a U.S. residual force in Afghanistan to look across the border to Pakistan," King said.

"But remember, for anyone who thinks this is impossible, it is improbable to have zero, but if you think it's impossible, I give you one example: Iraq -- everyone thought we'd leave a force there and we didn't."

The zero option is not without precedent for Obama.

The refusal by the Iraqi government to extend legal protections for U.S. troops after the end of the war there was a major reason the American military left the country with no residual military training force.

The other part of the equation is Obama's relationship with his generals, King said.

"There's also a big debate about this within the Pentagon. The generals are debating how many troops to leave behind, what's the composition of the force. So the president is also serving notice to the Pentagon here -- 'I'm going to keep the zero option,'" King said.

The Pentagon clearly would like to leave some troops in the country and that has been the plan all along, CNN Senior Pentagon Correspondent Barbara Starr said. "But if Karzai won't negotiate an arrangement, then they simply can't stay."

Perhaps the biggest loser in the standoff could be the intelligence community, which would need to keep tabs on al Qaeda in Afghanistan and Pakistan without the help of U.S. forces on the ground.

Logistically, it is possible to get all U.S. troops out of the country by the end of 2014 but those decisions would need to be made now.

"We need to know sooner rather than later," a U.S. Army official told CNN.

If Obama were to order a complete pullout, then the Army would have to establish schedules for troop withdrawals, shutting down bases, and shipping home equipment over the next 18 months, said an Army official who asked not to be identified because no decisions have been made.

It would also change schedules for troop rotations -- the Army is getting to the point that it would need to even out its schedule so that there aren't troops headed to Afghanistan late in 2014 only to come home a few months later, the official said.

Ultimately, the United States will make it's decision based on its own national security interests, Labott said.

"They aren't going to make a decision like that based on whether Karzai is more frustrating than usual - especially since they always find him frustrating," she said. "Not having any troops in Afghanistan -- particularly special forces -- adjacent to Pakistan and Iran, among others would put the U.S. at a strategic disadvantage."