As the United States and the United Kingdom contemplate further troop withdrawals from Afghanistan, any negotiated settlement is likely to involve more contact with the Taliban.

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US President Barack Obama will unveil plans later today for a significant reduction in US troop levels in Afghanistan.

In a televised address from the White House, he is expected to announce that 5,000 troops will leave Afghanistan by the end of July and up to 5,000 more by the end of 2011.

President Obama could also commit to the withdrawal of another 20,000 troops by the end of 2012, bringing the total to 30,000 - equivalent in number to the troop "surge" he signed off in 2009 at the start of his presidency.

Ahead of the 2012 US presidential election campaign, White House advisers are promoting the idea of an accelerated US pull-out from Afghanistan. Democratic and Republican politicians are united in the need to curtail a military mission costing $110bn a year.

But US Defense Secretary Robert Gates is leading the calls for a slower "drawdown" of the American presence in the country. The United States has suffered a total of 1,632 fatalities since the start of Operation Enduring Freedom in 2001. And Pentagon officials have voiced concern that a rapid withdrawal would compromise gains made against the Taliban.

Choreographed drawdown

The expected announcement by President Obama also has implications for the British presence in Afghanistan, where there have been 9,500 UK troops since the end of 2009.

The UK Government is anxious to conduct withdrawals in close co-operation with the US and other ISAF allies, which means that any drawdown will have to be carefully choreographed.

If President Obama confirms the pullout next year of an extra 20,000 troops, there will be strong pressure in this country to make a comparable-scale reduction - in the thousands rather than the hundreds.

The politics of any drawdown from Afghanistan will have to be carefully choreographed.

Prime Minister David Cameron has pledged that 450 British personnel will leave Afghanistan this summer, but there have been widespread calls for this number to be increased. The UK has suffered 374 fatalities in operations in Afghanistan since 2001.

UK and US fatalities in Afghanistan, 2001-2010