He warned that the deal could have dire long-term consequences for the region.
 

President Hamid Karzai's spokesman, Homayun Hamidzada, said Pakistan should take into consideration the "negative impact" of the deal.
 

The Pakistani president signed a bill introducing Islamic Sharia law to the Swat region on Monday.
 

Criticised
 

"We do not interfere in Pakistan's internal affairs," Mr Hamidzada told reporters in response to a question about the deal.
 

Pakistani politicians hope the deal will end a two-year insurgency

But he said there were concerns that "dealing with terrorists and handing over parts of one country to terrorists could have dire consequences in the long term".
 

"Since any deal with terrorist groups can affect our people and our country's security, we request Pakistan, before any such deals, take into consideration its negative impacts on relations between the two countries," he said.
 

The implementation of Islamic justice in the Swat valley was agreed in February in return for an end to the Taleban insurgency.
 

Mr Zardari had previously resisted signing the deal, which has been criticised by his Western allies.
 

There are concerns it could lead to human rights abuses and provide help to militants in the region.
 

But Pakistani Prime Minister Yousuf Raza Gilani said parliament had committed itself to implementing the Sharia system.
 

The bill introduced Sharia courts in the troubled Malakand division, comprising six north-western districts including Swat.
 

Sharia courts have already begun operating in the region. They have been welcomed by many in the region as a quick and efficient means of justice.
 

Swat is mostly under Taleban control. Thousands of people have fled and hundreds of schools have been destroyed since they began their insurgency there in 2007.
 

However, there have also been reports of controversial punishments.

From the outset of the deal, the US feared it might "become a surrender" to militants.