Depicting a grim future for Afghanistan without U.S. help, the top U.S. military officer said Wednesday that Afghanistan’s refusal to sign a security agreement with the United States may make the fight more difficult this year, embolden the enemy and prompt some Afghan security forces to cooperate with the Taliban to “hedge their bets.”

Army Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, spent the day with his commanders and troops in Afghanistan working to manage the after-effects of President Barack Obama’s order Tuesday to begin actively planning for a total withdrawal of U.S. troops by the end of the year.

In back-to-back meetings, he urged them to focus on the considerable military work they have to do and not worry about next year.

Dempsey said the possible exit of all U.S. troops was making Afghan military leaders anxious and eating away at their troops’ confidence. He said he spoke with some Afghan leaders after the Tuesday announcement, and they asked him to stay committed to an enduring U.S. presence, and told him they were doing all they could to get the agreement signed.

Frustrated with Afghan counterpart Hamid Karzai, Obama ordered the Pentagon to accelerate planning for a full U.S. troop withdrawal from Afghanistan by the end of this year. But Obama is also holding out hope that Afghanistan’s next president, to be elected this spring, may eventually sign a stalled security agreement that could prevent the U.S. from having to take that step.

The administration would like to leave up to 10,000 troops in Afghanistan after combat operations end on Dec. 31 to continue training Afghan forces and conduct counterterrorism missions. But without the agreement that would give international forces legal standing to stay in Afghanistan, Obama has threatened to pull all troops out, and NATO forces would follow suit.

Obama spoke Tuesday with Karzai, the first direct conversation between the two presidents since last June. Karzai has refused to sign the pact.

The impasse is having an effect, Dempsey said.

“It is having an effect on the enemy and in some ways I think encourages them, and intelligence supports that,” Dempsey told reporters. And, he said, the uncertainty of a continued U.S. presence in Afghanistan may encourage Afghan security forces in some parts of the country to “hedge their bets.”

“There are parts of the country where it seems to be, there will — with some likelihood …be some accommodations between the Afghan security forces and the Taliban,” said Dempsey. “I think a delay in the (security agreement) might accelerate those kind of accommodations. I don’t think it will be widespread by the way, but we do have to be alert to that possibility.”

He also said he expects that the Taliban will become more aggressive during the coming summer fighting season. Noting that the Afghan forces were in the combat lead last year for the first time, he said they did well. “So I think the Taliban has always calculated that they need to up their game this year to confront what they now realize is a pretty credible opponent.”

He added that while the U.S. can wait until after the spring elections before deciding whether to withdraw all forces, that decision will have to be made sometime in the summer.

“We have a pretty clear understanding of, at what pace they must progress in order to — if it became necessary — to empty the (war) theater by the end of the year,” Dempsey said.

Obama’s announcement after his conversation with Karzai appeared aimed at marginalizing Karzai’s role in the high-stakes negotiations over the future of the lengthy U.S.-led war. The Afghan leader has deeply irritated Washington with anti-American rhetoric, and with his decision this month to release 65 prisoners over the objections of U.S. officials.

The White House insists it won’t keep any American troops in Afghanistan after December without a security agreement giving the military a legal basis for staying in the country. While the White House did not publicly set a deadline for finalizing the agreement before that time, officials said the size and scope of any U.S. mission could shrink the longer Obama waits.

While Dempsey visited commanders, Defense Secretary Chuck Hagel met his NATO counterparts in Brussels this week. And NATO Secretary-General Anders Fogh Rasmussen said the 19,000 troops from other countries would also pull out of Afghanistan after year’s end without a security agreement.

“Let me stress, this is not our preferred option,” Rasmussen said. “But these are the facts.”