ISLAMABAD: Afghanistan's Taliban says it has suspended ''mediation'' with the United States to exchange captive US soldier Sgt. Bowe Bergdahl for five senior Taliban prisoners held in US custody in Guantanamo Bay, halting, at least temporarily, what was considered the best chance yet of securing the 27-year-old's freedom since his capture in 2009.

In a terse Pashto language statement emailed to the Associated Press on Sunday, Zabihullah Mujahed blamed the ''current complex political situation in the country'' for the suspension.

Bergdahl, of Hailey, Idaho, was last seen in a video released in December, footage seen as ''proof of life'' demanded by the United States.

Bergdahl is believed to be held in the border regions between Afghanistan and Pakistan.

Mujahed said the indirect talks with the United States had been mediated by the Middle Eastern state of Qatar, where the Taliban established a political office last June.

The video of Bergdahl was part of the negotiations which were to lead to the eventual transfer of five senior Taliban leaders held since 2002 in Guantanamo Bay.

''The leadership of the Islamic Emirate has decided to suspend the process for some time due to the current complex political situation in the country,'' according to the statement. ''The process will remain suspended without the exchange of the prisoners until our decision to resume.''

The Taliban spokesman did not elaborate on what ''political situation'' in Afghanistan led to the suspension of talks or say when they might resume. Afghanistan is in the middle of a presidential election campaign.

President Hamid Karzai cannot seek another term in office under the Afghan constitution which allows only two terms as president.

The election is scheduled for April 5.

The US State Department has refused to acknowledge the negotiations, but a US official familiar with the negotiations confirmed to The Associated Press that indirect talks were underway.

He requested anonymity because he was not authorised to speak to the media.

In response to the Taliban statement, US Embassy Spokesman in Kabul Robert Hilton said: ''Sgt Bergdahl has been gone far too long, however we can't discuss the efforts we're taking to obtain his return.''

Efforts at a swap are also seen as a concession to Karzai.

Washington would like to see him back away from his refusal to sign a security pact that is necessary for the United States to leave a residual force behind in Afghanistan Karzai he wants Washington to push reconciliation between the warring factions forward, without offering specifics.

The five Taliban detainees at the heart of the proposal are the most senior Afghans still held at the prison at the US base in Cuba. Each has been held since 2002.

They include: Mohammad Fazl, whom Human Rights Watch says could be prosecuted for war crimes for presiding over the mass killing of Shia Muslims in Afghanistan in 2000 and 2001 as the Taliban sought to consolidate its control over the country.

Abdul Haq Wasiq, who served as the Taliban deputy minister of intelligence and was in direct contact with supreme leader Mullah Omar as well as other senior Taliban figures, according to military documents. Under Wasiq, there were widespread accounts of killings, torture and mistreatment.

Mullah Norullah Nori, who was a senior Taliban commander in the northern city of Mazar-i-Sharif when the Taliban fought US forces in late 2001. He previously served as a Taliban governor in two northern provinces, where he has been accused of ordering the massacre of thousands of Shias.

Khairullah Khairkhwa, who served in various Taliban positions including interior minister and a military commander and had direct ties to Mullah Omar and Osama bin Laden, according to US military documents.

His US lawyers have argued in court papers that his affiliation with the Taliban was a matter of circumstance, rather than ideology, and that he had backed away from them by the time of his capture.

His lawyers also have argued that he was merely a civil servant and had no military role, though a judge found otherwise and said there was enough evidence to justify holding him at Guantanamo. His lawyers have appealed.

Mohammed Nabi, who served as chief of security for the Taliban in Qalat, Afghanistan and later worked as a radio operator for the Taliban's communications office in Kabul and as an office manager in the border department, according to US military documents.

In the spring of 2002, he told interrogators that he received about $500 from a CIA operative as part of the unsuccessful effort to track down Mullah Omar.

When that didn't pan out, he says he ended up helping the agency locate al Qaeda members.