US special envoy for Afghanistan and Pakistan Richard Holbrooke visited northwest Pakistan's tribal region on Wednesday, where security forces have been battling Islamist militants, officials said.

Holbrooke arrived in Pakistan late on Monday at the beginning of his first visit to the region since his appointment and met top government and military leaders on Tuesday.

'He went to the headquarters of the Mohmand Rifles and was given a briefing about military operations,' said a government official in the region, who declined to be identified, referring to a paramilitary force in the Mohmand region.

An intelligence agency official in the northwest said Holbrooke had travelled to Mohmand, one of the seven ethnic Pashtun tribal regions bordering Afghanistan, by helicopter.

President Barack Obama named Holbrooke as his special representative for Afghanistan and Pakistan last month, handing one of the most arduous US security challenges to the man who brokered the 1995 agreement that ended the Bosnian war.

He faces a host of challenges in dealing with the war in Afghanistan and an intensifying insurgency in northwest Pakistan while trying to ensure tension between old rivals India and Pakistan doesn't exacerbate the difficulties.

Holbrooke is also due to visit Afghanistan and India. A US embassy spokesman declined to comment on what Holbrooke was doing on Wednesday.

'As Ambassador Holbrooke said, he is in Pakistan to listen and learn the ground realities of this critically important country,' said embassy spokesman Lou Fintor. 'This was the focus of his discussions,' he said, referring to Holbrooke's talks on Tuesday with President Asif Ali Zardari, army chief General Asfaq Kayani and other top political and security officials.

Fintor said Holbrooke would report his findings to Obama and US Secretary of State Hillary Clinton.

The US administration is moving to complete its review of Afghan strategy before Nato holds its next summit on April 2.

Obama said this week there was no doubt terrorists were operating in safe havens in the tribal regions of Pakistan and the United States wanted to make sure Islamabad was a strong ally in fighting that threat.

With Afghanistan in the grip of the worst violence since the Taliban were toppled from power in late 2001, the US military has drawn up plans that could almost double the number of US troops there to about 60,000. - Reuters