Afghan President Hamid Karzai on Sunday said his country has the right to send troops into Pakistan to fight Taliban insurgents who launch cross-border attacks.

Speaking at a news conference in the Afghan capital, Kabul, Karzai threatened to send the troops after Pakistan-based Taliban leader Baitullah Mehsud, who vowed in May to send fighters into Afghanistan to wage war on foreign troops.

There are currently tens of thousands of foreign troops in Afghanistan, including about 2,500 Canadians, as part of the International Security Assistance Force created after a U.S.-led invasion toppled the former Taliban government in 2001.

Karzai said Afghanistan has the right to self-defence when it comes to the cross-border attacks.

"When they cross the territory from Pakistan to come and kill Afghans and kill coalition troops, it exactly gives us the right to go back and do the same. Therefore, Baitullah Mehsud should know that we will go after him now and hit him in his house," he said.

"And the other fellow, [Taliban leader] Mullah Omar of Pakistan should know the same," Karzai continued. "This is a two-way road in this case, and Afghans are good at the two-way road journey."

Karzai has previously pleaded to international forces to confront militants in Pakistan, but this was the first time he has threatened to send Afghan troops across the border.

"We will complete the journey and we will get them and we will defeat them. We will avenge all that they have done to Afghanistan for the past so many years," he said.

In Pakistan, Prime Minister Yousuf Raza Gilani said his country is a sovereign state that wants good relations with its neighbours.

But he said the Afghan-Pakistan border is too long to prevent people from crossing, "even if Pakistan puts its entire army along the border."

"Neither do we interfere in anyone else's matters, nor will we allow anyone to interfere in our territorial limits and our affairs," Gilani told the Associated Press. "We want a stable Afghanistan. It is in our interest."

With files from the Associated Press