The Nato allies decided to hold alliance troop levels in Afghanistan steady at about 12,000 next year and launched a campaign to fund the 350,000 Afghan forces it hopes can some day secure the country against Taliban militants.

Fourteen years after the United States first sent troops to Afghanistan, Nato governments have doubts about the ability of its army and police to defend against Taliban fighters, who briefly took over the northern city of Kunduz in September.

As a result, the 28-member Western alliance is abandoning plans to slash its troop levels by the end of this year.

"We are in Afghanistan to prevent that Afghanistan again becomes a safe haven for international terrorists ... that is also in our security interest to make sure that that doesn't happen," Nato Secretary-General Jens Stoltenberg said at a meeting of Nato foreign ministers.

Excluding U.S. counter-terrorism forces, Nato will have about 12,000 troops in Afghanistan for most of next year, made up of about 7,000 US forces and 5,000 from the rest of Nato and its partners such as non-Nato member Georgia.

Allies also launched a campaign to raise about $3 billion euros to help pay for Afghanistan's state security forces from 2018.

The Afghan security forces budget, funded by the United States and its Nato allies, is agreed up to the end of 2017. Nato wants to announce further funding for the 2018-2020 period at its next leaders summit in July.

"Afghanistan is still one of the poorest countries in the world, so I think this is a good investment we are making," Stoltenberg told a news conference.

As agreed at the Nato summit in Chicago in 2012, non-U.S. Nato allies and partners such as Japan give a total of $1bn a year in addition to the $4.1bn that the United States spends on Afghan security forces every year.

The Taliban's brief takeover of a provincial capital in late September has shaken confidence in the ability of Afghan forces and both the United States and its Nato allies now say events, rather than timetables, must dictate gradual troop reductions.

US President Barack Obama had aimed to withdraw all but a small US force before leaving office in January 2017, pinning his hopes on training and equipping local forces to contain Taliban militants fighting to return to power.