Updated

President Barack Obama's special envoy to Pakistan said Thursday that securing hard-fought gains in the Swat Valley and ensuring the safe return of refugees uprooted by the government's anti-Taliban campaign should be Islamabad's top priority.

Pakistan's military is winding down an offensive that began in late April in the country's northwest and displaced some 2 million people from Swat and surrounding areas, according to the United Nations.

"The highest priority right now has to be to secure the areas in Swat and Buner as the refugees return," Richard Holbrooke told reporters after a two-day visit in the Pakistani capital.

Security forces have also been carrying out strikes ahead of a promised new offensive in nearby South Waziristan, part of Pakistan's lawless tribal belt along the Afghan border. The military says that operation is aimed at eliminating Pakistani Taliban leader Baitullah Mehsud, who heads a loose alliance of militant groups based in the tribal areas.

Mehsud has been blamed for orchestrating scores of suicide attacks across the country, and Islamabad considers him Pakistan's greatest internal threat.

Holbrooke said the U.S. has been slow in recognizing the importance of Mehsud, but stressed Thursday that eliminating him was "without a doubt" of strategic importance to the United States.

"I think Baitullah Mehsud is one of the most dangerous and odious people in the entire region and the United States paid insufficient attention to him until very recently," Holbrooke said.

Although the military has declared Swat cleared of most militants and civilians have been returning to the region for the past two weeks, violence persists in the region. On Thursday, security forces killed six suspected militants in a shootout near the main city of Mingora, said Col. Akhtar Hussain.

Authorities suspended the refugee return for a day Thursday, although the reason given was unconnected to the security situation. Lt. Col. Waseem, the military spokesman for the Swat operation, said it was to allow workers helping the displaced to have a break. He said nearly 40 percent of those who fled their homes have returned over the past two weeks.

Swat was once a popular tourist destination known for its Alpine scenery. In recent years, it fell under the sway of Taliban militants led by radical cleric Maulana Fazlullah.

While Holbrooke welcomed the refugee return, he noted that parts of the region were still problematic.

"Northern Swat is still insecure. And the leadership like Fazlullah has not been captured. So there's a long way to go here," he said.

Critics have noted that Pakistan's authorities have concentrated on eliminating certain Taliban militants, such as Mehsud, while apparently allowing other militant groups to operate.

But Holbrooke said no country could tackle every problem simultaneously.

"By necessity the Pakistanis have to focus on priorities. They couldn't go after everyone at once," he said.

"I think what they're doing makes a lot of sense. They're going after the people who pose the greatest threat to their own nation. And who also pose a great threat to the international forces across the border in Afghanistan. That makes sense to me."