Gen. Petraeus: Progress in Afghanistan 'Fragile and Reversible'

VIDEO: Petraeus on Afghanistan: Fragile and
WATCH Petraeus on Afghanistan: 'Fragile and Reversible'

The top U.S. commander in Afghanistan acknowledged today that security in the war-torn country is still fragile but warned that it would be unwise to abandon the mission, despite the U.S. public's record-high opposition to the war.

Speaking to the Senate Armed Services Committee, Gen. David Petraeus said "much difficult work lies ahead with our Afghan partners" to expand gains achieved in the past year.

"As a bottom line up front, it is ISAF's [International Security Assistance Force] assessment that the momentum achieved by the Taliban in Afghanistan since 2005 has been arrested in much of the country and reversed in a number of important areas," Petraeus said in his first congressional appearance since he took command last summer.

"However, while the security progress achieved over the past year is significant, it is also fragile and reversible."

Public support for the war in Afghanistan has dropped sharply in recent months amid domestic economic and employment woes. Thirty-one percent now say the war in Afghanistan has been worth fighting, a new low, 64 percent say it's not worth fighting, and 49 percent feel that way "strongly," according to an ABC News-Washington Post poll released today. The latter numbers are both record highs in the poll.

With lawmakers already under pressure to show results on the jobs and economic front, the numbers don't bode well for politicians.

When asked to respond to the poll, Petraeus -- who is well respected on both sides of the political aisle -- acknowledged the frustration but reminded senators of the original mission of the war.

"We have spent an enormous amount of money, we have sustained very tough losses and difficult life-changing wounds," he said. "But I think it is important to remember why we are there at such a time. It's important to remember that's where 9/11 began. It's where the plan was made. ... That is where al Qaeda had its most important sanctuary in the world."

A January report painted a gloomy picture of the war in Afghanistan, the longest in U.S. history. Attacks by insurgents have increased by two-thirds above already record levels in 2009, the "highest annual growth rate we have recorded," the Afghanistan NGO Safety Office said, adding that "their momentum would appear unaffected by U.S.-led counterinsurgency measures."

The report argued that the White House and the U.S. military's claims of success are overstated.

Now, the onset of spring has once again elevated concerns about a Taliban resurgence, especially from safe havens on the border with Pakistan. And with public opposition escalating to a new record, even supporters of the war are viewing the situation with caution.

"The cost of our commitment to this conflict remains substantial, especially of precious lives we have lost," said Sen. John McCain, R-Ariz., the ranking member on the committee. "And according to one new poll ... a majority of Americans no longer support the war. The next several months will therefore be decisive as winter turns to spring, the traditional fighting season in Afghanistan."

War in Afghanistan Under Spotlight as Public Opposition Escalates

But supporters of the war say the United States must continue the work it started in Afghanistan 10 years ago.

"I think we all know from experience you can't make decisions about war and peace based on public opinion," said Sen. Joseph Lieberman, the independent from Connecticut. "Once you commit to a cause, as we did after 9/11, to the cause of a different new Afghanistan and you commit troops to it, you can't be affected by waves of public opinion."

"We are succeeding in Afghanistan today, so I think the downward turn in the public opinion here in the United States has more to do with the understandable preoccupation of the American people with the economy, with jobs, with the deficit," he added.

"In that sense, I think we have to come back and remind the American people of why we are in Afghanistan. Why it is worth it and that we are now succeeding."

President Obama has committed to a draw-down of U.S. troops in Afghanistan, starting July, and transitioning security responsibilities to Afghan forces. Petraeus today said he supports that plan and will present his options and recommendations to the president on how to go about reducing the number of troops.

But that could be a significant challenge in itself. As ABC News reported Monday, field commanders in Afghanistan are asking for more troops and are openly challenging the wisdom of withdrawing any U.S. forces by the July 11 date set by the administration.

There is also concern among Afghans about joining the police and army because of security reasons, despite a hefty salary. On Monday, a suicide bomber posing as an army volunteer blew himself up at an army recruiting center in northern Afghanistan, killing at least 35 people and marking the second such attack on the center.

A broad and bipartisan 73 percent of Americans say the United States should withdraw a substantial number of its combat forces from Afghanistan this summer, but 39 percent think it will, according to ABC News-Washington Post poll.

Some lawmakers plan to draft a resolution calling on the president to withdraw all U.S. forces from Afghanistan no later than Dec. 31, 2011, but that's likely to fail, as it has in the past.

ABC News' Mike Gudgell, Nick Schifrin and Gary Langer contributed to this report.