Significant increase in the Haqqani network activity in Khost, Paktia, Logar and Wardak has been reported which are on infiltration routes from Pakistan to launch attacks against the Afghan capital, CNN reported quoting top NATO officials in Kabul.
"Whether or not NATO and US will have to provide more assistance to the Afghan forces along the border with Pakistan," the officials said would depend on "the level of threat coming out of Miranshah".
General John Allen, the commander of US and NATO forces in Afghanistan, has completed a 90-day assessment of the campaign plan and suggested a gradual shift of focus to pulverise Haqqani network militants in the east.
"As things improve in the south, we will focus more on the east," officials said.
Though US officials have given bare details about the build-up to launch the new operation against the Haqqani terror network, Pakistani media reports have said that heavy artillery, fresh troops and helicopter gunships have been moved closer to the border to hit Haqqani terror network`s stronghold in the region.
The new Afghan operation in the east against the Haqqani militants comes as Pentagon said that cross-border attacks emanating from Pakistan against US-led forces in Afghanistan have increased since the US raid that killed Osama bin Laden in Pakistan.
New York Times reported that US bases in Afghanistan`s eastern Paktika province had complained that rocket fire had dramatically increased from Pakistani territory since May.
It was unclear if the fire, usually 107mm rockets, was the result of an emboldened insurgency, retaliation by the Pakistani military or some mixture of both, the Times reported, quoting US military officers.
In some cases the rocket fire came from insurgent positions just inside Afghanistan, with crews then rushing back across to Pakistan, the newspaper wrote.
There were at least 102 "close-border" attacks against three US outposts in Paktika since May, compared to 13 such incidents during the same period last year, it said.
When contacted by US troops, Pakistani military officers at the border often say they are not aware of the rocket fire or cannot see it, even though the fire is often coming from positions next to Pakistani military or Frontier Corps posts, the Times reported.
Given the degree of sophistication and coordination displayed in the attacks, some US officers strongly suspect the Pakistani military or intelligence service is involved in the rocket fire, the paper said.
The rise in cross-border fire comes amid deep strains in US-Pakistan relations in the aftermath of the bin Laden raid and following accusations from former top US military officer Admiral Mike Mullen that Islamabad was supporting Haqqani militant attacks on US forces in Afghanistan.