The U.S. military is waiting to see whether some Taliban leaders take a break during August for Ramadan, crossing over the border into Pakistan after several weeks of high profile attacks.

"There's an awful lot of discussion about the Taliban leadership leaving their fighters here, and particularly to go back across the border for Ramadan," Admiral Mike Mullen, the top U.S. military officer, referring to talks he had with U.S. commanders in Kandahar and Helmand provinces.

"We'll see whether they do that or not," he told reporters travelling with him in Afghanistan.

The Muslim fasting month of Ramadan will start on Monday in Afghanistan. It is a lunar month, but this year coincides almost exactly with the month of August on the Gregorian calendar used in most of the West.

The military assessment about Taliban movements follows a string of high-profile attacks and assassinations that have shaken southern Afghanistan.

The strikes have been particularly acute in Kandahar province, the Taliban's birthplace.

A suicide bomber killed the mayor of Kandahar on Wednesday, compounding fears of a dangerous power vacuum in Afghanistan's south in the wake of the assassination of President Hamid Karzai's half-brother, Ahmad Wali Karzai.

Mullen acknowledged a degree of political instability because of the assassinations but added U.S. commanders had not reported a deterioration in day-to-day security in Kandahar.

"At least from the commander's standpoint, they haven't seen that," said Mullen, who flew into Kandahar on Friday.

DRAWDOWN PLAN BY OCTOBER

Mullen, on what may be his last trip to Afghanistan before stepping down at the end of September, has been upbeat about battlefield progress and the ability of the U.S. military to maintain its momentum even as it carries out a withdrawal ordered by President Barack Obama last month.

Obama's decision to withdraw 33,000 of the nearly 100,000 U.S. forces in Afghanistan by the end of next summer was a faster timetable than Mullen had initially recommended. The goal is to handover lead security responsibility to Afghan forces by the end of 2014.

"I'm very confident we can meet the needs on the ground as well as the deadlines and the goals that have been laid out by the president," Mullen said.

The new U.S. commander in Afghanistan, Marine Corps General John Allen, is still drawings up plans for the drawdown of the first 10,000 forces by the end of the year, a small number of which pulled out earlier this month. Mullen disclosed that Allen had until mid-October to come up with that plan.

The U.S. military chief renewed his concerns about corruption and a lack of governance in parts of Afghanistan. He said U.S. military commanders he had met with expressed a "very stark view" of corruption in the country.

"I'm talking about the criminal patronage network and how they are woven into the fabric of how things get governed," Mullen said.

He said the matter needed to be addressed throughout the Afghan government but also said the U.S. embassy in Kabul "is going to have to move on that as well".