The Obama administration is considering setting up a new military base in Iraq's Anbar province and is closing in on a decision to send several hundred more trainers and advisers to help Iraqi forces in the fight against Islamic State militants there, U.S. officials said on Tuesday.

While final approval from President Barack Obama is still needed, the modest military expansion in Iraq appeared the likeliest choice among a range of options he is weighing to bolster a struggling Iraq effort against insurgent forces in Anbar in the country's Sunni heartland.