Pakistan summoned the U.S. ambassador to reject allegations in a Pentagon report that Islamabad supports militant proxies in neighbouring India and Afghanistan, a foreign ministry statement said Thursday.

It said Pakistani National Security and Foreign Affairs adviser Sartaj Aziz conveyed the complaint to U.S. Ambassador Richard Olson in a meeting at the ministry.

The U.S. Defence Department report, titled "Progress Towards Security and Stability in Afghanistan," said militants continue to enjoy safe havens in Pakistan, which uses the fighters as a hedge against its loss of influence in Afghanistan and as a counterweight to India's superior military.

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The statement says the allegations are of particular concern now, given that the Pakistani military is waging a major offensive against militants in North Waziristan, a tribal region bordering Afghanistan. Pakistan launched the long-awaited operation in June, following years of allegations that it was turning a blind eye to militants who launch cross-border attacks on Afghan and NATO security forces.

Islamabad has always denied the allegations, and has accused Kabul of hosting militants that carry out attacks in Pakistan.

The Pentagon report lauded the latest military push and acknowledged that the army had made gains against local and foreign militants. But the Pakistani statement said the report was "unsubstantial" while noting Pakistan's co-operation with the U.S. in areas of mutual interest.

Pakistan has been at war for more than a decade with the Pakistani Taliban, an offshoot of the Afghan extremist group Islamabad had supported in the past. Last weekend a suicide bomber set off his explosives near a Pakistani paramilitary checkpoint on the border with archrival India, killing 61 people.

Pakistani army chief Raheel Sharif is visiting Kabul on Thursday to meet the new Afghan President Ashraf Ghani and senior military leaders.