BRUSSELS - Iran could improve its chances of playing a role on the sidelines of Syria peace talks this month by working with Damascus to stop the bombardment of civilians and improve humanitarian access, US officials said on Monday.

"There are ... steps that Iran could take to show the international community that they are serious about playing a positive role," one of the officials said in Brussels.

"Those include calling for an end to the bombardment by the Syrian regime of their own people. It includes calling for and encouraging humanitarian access." Another official made clear that the comment on bombardment referred to Syria's biggest city, Aleppo.

However, one US official said Washington still believed it was "less likely than likely" that Iran would play any role at the Jan. 22 peace conference on Lake Geneva in Switzerland, even on the sidelines.

Another official said Iran and the United States had not discussed the matter directly. All the officials declined to be named.

US Secretary of State John Kerry on Sunday reiterated US opposition to Iran being a formal member of the so-called "Geneva 2" talks because it does not support the 2012 international agreement on Syria, dubbed "Geneva 1".

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