The prospect of peace in Afghanistan raises its own risks to rebuilding efforts, a US watchdog said on Thursday, citing reintegrating Taliban fighters, spurring the economy and protecting women's rights as major issues to be dealt with.

“A peace agreement would be welcomed by the long-suffering Afghan people,” the Special Inspector General for Afghanistan Reconstruction (SIGAR) John Sopko said in Washington.

“But it could bring its own challenges to sustaining what the United States, coalition partners and the Afghan government have achieved.”

The United States has spent $132 billion since 2002 on training Afghan forces, strengthening institutions and other initiatives.

US-led forces deposed the Taliban in 2001 after the September 11 attacks in the United States but the militants regrouped and have steadily extended their influence during 17 years of war.

Peace talks between US and Taliban officials began late last year, raising hopes for an end to the conflict. The latest round ended this month with both sides citing progress.

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Even if the war with the Taliban ends, Afghanistan may remain insecure because of the presence of other militant groups, Sopko's office said in a report to US Congress and the secretaries of state and defense.

Congress created the office to oversee US-led reconstruction efforts in Afghanistan.

Reintegrating the Taliban, whose Islamic views are more conservative than those of much of the population, would be a particular challenge, SIGAR said.

About 60,000 fighters are likely to find few job opportunities in a weak economy, it said.

Lasting peace could improve economic growth but in the short term, some 2 million Afghans living in Pakistan may return, adding job-seekers into a weak labour market.

While the Taliban has said in official statements they might consider more liberal policies towards women, their chief negotiator has said the constitution, which protects women's rights, is an obstacle to peace, SIGAR wrote.

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Such a stance could jeopardise the economic and political freedoms Afghan women have achieved.

More of the US reconstruction effort has gone into the Afghan National Army than to its national police, and a strategy for a “competent” police force, sustained by foreign assistance, would also be required, SIGAR wrote.

Endemic corruption has hampered reconstruction, and remains the “top strategic threat” to the government's legitimacy, it said.

A burgeoning illicit opium trade also jeopardises security, governance and development.