Meanwhile, the attorney for Staff Sgt. Robert Bales, accused of killing the 16 civilians, prepared to meet his client for the first time Monday, CNN reported.
If U.S. troops can't resume their missions and can't return to villages as Afghan President Hamid Karzai called for, "the United States' mission is changed," Maj. Gen. James A. "Spider" Marks told CNN.
Karzai made his demand after the March 11 shootings in two neighboring villages near a U.S. outpost in the Panjwai district in Kandahar province. Karzai demanded troops withdraw from villages and return to their bases and said U.S.-Afghanistan relations were "at the end of their rope." The incident -- which followed the burning of Korans on a U.S. base and U.S. personnel urinating on corpses of Taliban fighters -- stoked anti-American sentiment in the country.
"Our commanders on the ground will determine that probably within about another week," Marks said. "Within a couple of weeks, it would not be unusual if there has not been a change in our posture inside those bases, that you can see forces coming back. It's not inconceivable that that could happen."
Karzai is pushing for the NATO-led International Security Assistance Force transition security responsibilities to Afghan forces by 2013, a year ahead of an agreed-upon plan.
President Obama re-emphasized he intends to adhere to the NATO-set timetable even as he faces growing demands to bring troops home early.
Bales is being held at the U.S. military prison at Fort Leavenworth, Kan.
"You couldn't imagine a more difficult case, I don't think," John Henry Browne, Bales' civilian attorney, told reporters Sunday. "This case has political ramifications. It has legal ramifications. It has social ramifications."
Afghans have demanded that Bales be returned to face trial in the country.
U.S. officials have said Bales left his outpost and carried out the slaughters alone. One villager told CNN there were several attackers and another said it was only one person.
However, Taliban leaders say they don't think Bales acted alone.
"We don't think that one American was involved," a Taliban commander, who spoke on condition of anonymity, told CNN. "The foreigners and the puppet regime [in Afghanistan] are blind to the truth of what happened here.
"But if this was the act of one soldier, we want this soldier to be prosecuted in Afghanistan, and according to Islamic law. The Afghans should prosecute him."
Prosecutors have said nothing publicly about the case against Bales, 38.
Obama said he instructed the military to prosecute it aggressively. Defense Secretary Leon Panetta said Bales could face the death penalty.
Formal charges are expected to be filed within a week.
Bales' defense team hasn't denied the charges against the married father of two, but point to his three tours in Iraq and one in Afghanistan, along with a traumatic brain injury and a severe foot injury, as possible mitigating circumstances.
"It is too early to determine what factors may have played into this incident and the defense team looks forward to reviewing the evidence, examining all of Sergeant Bales' medical and personnel records, and interviewing witnesses," Browne said in a statement.
Bales will also have at least one military lawyer, officials said.