QUETTA, Pakistan - A man described as the Taliban's new top field commander has vowed to liberate Afghanistan from "American slavery," a pro-Taliban cleric said Saturday.

Dadullah Mansoor made the remarks in an audiotape played Friday at a rally at Killi Nalai, a village about 72 kilometres west of Quetta near the Afghan border, said Abdul Sattar Chishti, the cleric who organized the event.

He said more than 12,000 people listened to the speech by the brother of Mullah Dadullah, the top Taliban commander who was killed in a U.S. operation last month in southern Afghanistan. It was not immediately possible to verify Chishti's claims.

He said Mansoor vowed to avenge his brother's death and those of others killed while fighting U.S., NATO and Afghan forces.

"The blood of my brother will never go waste. We will never forget his sacrifices, and the role of other martyrs. We will complete Dadullah's mission by expelling Americans and liberating Afghanistan," Chishti quoted Mansoor as saying.

He said Mansoor also asked youths to participate in holy war against infidels as emotional participants chanted slogans in favor of Taliban chief Mullah Omar and al Qaeda leader Osama bin Laden.

Pakistan is a key ally of the United States in its war on terror. It has deployed about 90,000 troops in its northwestern tribal areas to flush out remnants of the Taliban, al Qaeda and their local supporters.

Although pro-Taliban elders have held similar rallies in northwestern tribal regions, protests the size of the one organized in Killi Nalai are rare.

Pakistan used to be a main supporter of the hardline Taliban militia before switching sides to join the U.S.-led war against terrorism following the Sept. 11, 2001, attacks in America. A U.S.-led invasion in Afghanistan ousted the Taliban government.

But Afghan and some Western officials have said Pakistan is providing Taliban militants with shelter, allowing them to launch attacks against Afghan government and coalition forces.

Pakistan denies the charges, and says it has done all it can to curb militancy.