The army has set up five bases in the region near the Afghan border to try to seal off the Taliban's main stronghold.
Military spokesman Gen Athar Abbas said troops were "carrying out a successful operation" in the region, which he described as "the centre of gravity of the whole terrorism problem" of Pakistan.
Gen Abbas said the operation would be completed "within the timescale" but that it would not be appropriate to say what that timescale was.
Reports from the region remain sketchy as the army is denying access to both foreign and Pakistani journalists within South Waziristan.
Meanwhile, US Central Command chief David Petraeus, who oversees the operations in Afghanistan and Iraq, is holding talks with senior Pakistani military officials in Islamabad.
FORCES IN WAZIRISTAN
Pakistan army: Two divisions totalling 28,000 soldiers
Frontier Corp: Paramilitary forces from tribal areas likely to support army
Taliban militants: Estimated between 10,000 and 20,000
Uzbek fighters supporting militants: several hundred
South Waziristan is considered to be the first major haven for Islamic militants outside Afghanistan since the 11 September 2001 attacks in the US and Pakistan's government has been under considerable pressure from the US to tackle militancy there.
US Senator John Kerry is currently meeting Pakistani leaders in Islamabad where he is expected to discuss America's multibillion-dollar aid package for Pakistan, amid concerns by some officials in the country that it comes with unacceptable strings attached.
'Consolidating'
Clashes between security forces and the Taliban have continued across the South Waziristan region, the BBC's Syed Shoaib Hasan reports from neighbouring Dera Ismail Khan.
ANALYSIS
Syed Shoaib Hasan, BBC News, Dera Ismail Khan
At the moment, the situation is a stalemate as the army tries to use ground troops backed by heavy weapons and air power to push back the Taliban.
The militants have entrenched themselves in fortified positions in the areas where the military is marching in. But they are likely to resort to traditional guerrilla tactics once the army is firmly inside territory controlled by the Mehsud tribe.
This is the heartland of the resistance, and it is here that the fate of the campaign will be decided.
Checkpoints and supply depots have been established in Sherawangai and Mandana in the south-west towards the Tiarza sub-division.
So far, the troops have advanced on the Jandola-Sararogha access and have secured Sherwam, Torghundai and Kotkai areas.
The army is reported to have blown up ammunition dumps - some hidden in caves.
Fighter jets have also been deployed to attack the Taliban in Makeen, Nawazkot, Spinkamar and Khaisora.
Meanwhile the army has taken control of the key Ingalmall mountain range, which marks the passage into Afghanistan.
This will play an important role in disrupting the militants' supply lines and in ensuring more help does not arrive from Afghanistan.
According to reports, the Taliban have been using heavy weapons to fire back at the troops.
'Getting nothing'
Hundreds of people from South Waziristan continue to arrive in Dera Ismail Khan to escape fighting.
Army spokesman Major General Athar Abbas: "Stiff resistance was met"
"I decided to leave when my neighbour's house was destroyed by jet fighters," Rahim Dad Mehsud, a labourer from Tiarza, was quoted as saying by the AFP news agency.
He said he had walked three days to get to Dera Ismail Khan with his 12 relatives.
The BBC's Aleem Maqbool, in Dera Ismail Khan, says there is very little preparation for the displaced people.
He adds aid agencies have told him they have been asked by the government not to give assistance to the displaced people because of fears it may be channelled back to help tribesman and militants.
The federal government and the military have ordered the closure of many schools and colleges for a week in Islamabad and some other cities for security reasons.
The move comes amid fears that militants may try to take hostages to force the authorities to ease pressure on their positions in South Waziristan, correspondents say.
Security is tight across Pakistan and police in Islamabad have searched a number of religious seminaries and some nearby rural areas for militants.
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