KANDAHAR AIR FIELD, Afghanistan—The U.S. military is leaning toward extending its mission in southern Afghanistan’s strategic Kandahar province into 2016 instead of wrapping up work at the massive regional base by the end of this year, defense officials said on Sunday.

No final decisions have been made, but top U.S. officials said new Defense Secretary Ashton Carter could decide to support a delay in winding up operations at Kandahar Air Field, a key benchmark in the U.S. pullout.

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