* NATO plans for post-2014 mission without detailed troop numbers
* Delay in negotiating U.S.-Afghan pact worries some allies
By Adrian Croft and Sabine Siebold
BRUSSELS, Oct 23 (Reuters) - NATO has agreed the outline of a military force it intends to keep in Afghanistan after its combat mission there ends next year, but troop numbers remain uncertain due to ongoing talks between Washington and Kabul.
NATO defence ministers endorsed a "strategic planning assessment" on Wednesday, setting out command and control arrangements and the capabilities needed for the mission that the alliance says will have a training and advisory role, U.S. and NATO officials said.
The alliance has 86,000 troops in Afghanistan, of which the majority are American. The combat mission is due to end by the end of 2014 with Afghan forces taking responsibility for fighting Taliban insurgents.
The United States will not say how many troops it intends to contribute to the new mission until it has sealed an agreement with Afghanistan setting out the terms under which U.S. forces will operate there after 2014.
Without an agreement, Washington says it could pull out all its troops at the end of 2014.
The obstacle has also stopped other NATO allies from announcing the size of their troop contributions, holding up detailed planning by NATO military chiefs.
Once the U.S.-Afghan agreement is sealed, NATO must negotiate a similar agreement with Afghanistan creating the legal basis for other NATO nations to keep troops there.
Although the document agreed on Wednesday lacks detailed troop numbers, NATO planners have worked on the assumption it will be between 8,000 and 12,000 soldiers.
"Our planning is on track. We make steady progress ... But of course we can't finalise our preparations until we have finalised negotiations on the legal framework," NATO Secretary-General Anders Fogh Rasmussen told reporters.
NO PANIC YET
One NATO diplomat said the original aim had been to approve a detailed operational plan, including troop numbers, by now.
NATO military planners have concerns about the dwindling time left to decide which NATO allies would commit what forces to the mission, "but they are telling us 'no panic yet'," said the diplomat, speaking on condition of anonymity.
Germany is one of the few countries to decide on a specific commitment after 2014, announcing in April it wanted to keep between 600 and 800 soldiers in Afghanistan.
However, Defence Minister Thomas de Maiziere said on Wednesday Germany was waiting for agreement on the U.S.-Afghan pact and a U.S. decision on troop levels.
"Our decision depends on these decisions. We have made an offer, but we need clarity on the rights and duties of our soldiers and we need clarity on the U.S. decision," he said.
De Maiziere also voiced annoyance at comments by Afghan President Hamid Karzai in a BBC interview that the NATO operation had caused "a lot of suffering" while not bringing security.
A spokesman for Karzai said on Sunday that Kabul and Washington had not yet agreed on several issues in the bilateral security pact. If no agreement was reached, he said, the draft would be put to a Loya Jirga, an assembly of Afghanistan's tribal elders, in November.
Afghan Defence Minister Bismullah Khan Mohammadi said in Brussels on Wednesday he hoped the bilateral security agreement would be signed by mid-November and said the NATO-Afghan deal might also be approved by the November Loya Jirga, or soon afterwards. (Additional reporting by Phil Stewart; Editing by Robin Pomeroy)