KABUL, Afghanistan (AP) — Fighting in Afghanistan may be considerably worse this summer than last, but some reduction in American forces is still possible in July, the top U.S. and NATO commander in the country said Wednesday.

Gen. David Petraeus told The Associated Press that he will present President Barack Obama with multiple plans, including different levels of troop reductions that accommodate Obama’s July target for starting a force drawdown.

He said the extra forces poured in by Obama have secured gains in Afghanistan, but he still described them as “fragile and reversible.” As Taliban fighters start trying to take back southern strongholds during the traditional spring and summer fighting season, violence may spike considerably, he said.

“Many intelligence estimates say that it will be as violent or perhaps even more violent” than 2010, Petraeus said in an interview at his office in Kabul.

“They will come back in force. There is some concern that there will be sensational attacks that could be indiscriminate in nature,” he warned.

Petraeus spoke ahead of a trip to Washington, where he is scheduled to testify on Capitol Hill next week. It will be his first testimony since he took over the Afghan command eight months ago.

Last year was the deadliest of the nearly decade-old war for coalition forces, with 701 killed, including 492 Americans. There have been fewer deaths in the first two months of this year — 68 compared to 92 last year. Four more were killed in March.

When Obama authorized a surge of 30,000 U.S. forces in late 2009, the plan was to help Afghan forces and the weak civilian government gain a foothold in the fight against the resurgent Taliban. Those troops arrived last summer, and Petraeus’ trip to Washington is seen by many as the time to determine if the plan has worked.

Petraeus said that he plans to tell Congress that the increase in NATO’s strength has led to gains in a relatively short time, particularly by taking out Taliban weapons caches in the south and limiting the insurgents’ freedom of movement there.

Petraeus argued that there has also been progress in transferring some responsibilities to Afghan authorities even in volatile southern provinces like Helmand and Kandahar, longtime Taliban strongholds. The additional Afghan strength should allow some U.S. force reductions, he said, though he would not say how many or where.

Petraeus said he would provide options in accordance with Obama’s intention to cut back the U.S. presence. “Those options will be varying levels of force reductions as we get closer to that time,” he said, pledging a specific recommendation before July but declining to elaborate.

The plan hinges on the ability to transfer security and government responsibilities to an Afghan administration still riddled by corruption and with little authority outside the capital. Petraeus acknowledged this as a challenge but said it was not insurmountable.

Petraeus said ,international missions are trying to accelerate programs to train both civilian administrators and security forces. “The key to that though, is of course that there be the development of sufficient Afghan capacity,” he added.

Afghan President Hamid Karzai plans to announce the first areas outside Kabul that will be transferred to Afghan control in a speech on March 21, the start of the Afghan new year. Karzai said earlier this week that he plans to name “five or six places,” without getting more specific.

That transition is key to providing a real exit strategy for international forces, which hope to transfer full oversight of security operations to Afghan forces by 2014. There are currently about 105,000 U.S. troops in Afghanistan, along with about 40,000 NATO troops from other countries.

“We would hope that by July we will have solidified and even expanded further the security bubbles, the security gains that have been achieved over the course of the last eight to 10 months in particular,” Petraeus said.

Transition is likely to be slow and rocky. Petraeus pointed to the capital city of Kabul, where the Afghan government and its forces already control security and administration, as a success story. But even well-defended Kabul has been hit by a two high profile suicide bombings in recent months. Installing civilian administrators in the volatile south has gone slowly, hampered by assassination campaigns.

Also, during this push, relations between Karzai and his American partners appear to be souring. Recent civilian casualties caused by NATO forces prompted Karzai to say apologies were no longer sufficient ,demanding a solution.

Petraeus said he continues to work to decrease civilian casualties and called civilian deaths at NATO’s hands tragic. There was a 26 percent drop in civilian deaths caused by coalition forces last year, despite an increase in fighting and more intense air and ground campaign against insurgents, according to a U.N. report released Wednesday.

The U.N. blamed insurgents for 75 percent of the 2,770 combat-related killings in 2010. The U.N. said insurgents were responsible for 2,080 deaths, a 28 percent increase from 2009, while U.S.-led forces were said to have killed 440 people.

Deaths from NATO strikes are the ones that spark protests from people angry that their supposed protectors are killing any innocent civilians.

As Petraeus meets with members of Congress, a main question that will likely continue to arise will be whether Karzai is a viable partner.

The general said he believes Karzai is committed to fighting corruption and the criminal networks that plague Afghanistan — including some that allegedly involve Karzai relatives — and that any rifts can be healed.

“What you’ve got to do is have good dialogue, have forthright discussions,” which Petraeus said he has with Karzai. The general arrived at Wednesday’s interview straight from Karzai’s palace, where he said they dug into topics like how to deal with politically backed crime bosses.

Petraeus dismissed questions about how long he would remain in his post, which is a step down from his previous one as head of Central Command.

“I’m committed to this mission. This is my focus,” Petraeus said, saying his key is, “Go into this thinking this is your last job.”