NATO chief Jens Stoltenberg said Tuesday the alliance was working on new support measures for Turkey, but insisted the commitment predated Ankara's shooting down of a Russian jet on the Syrian border, AFP reports.

Speaking as foreign ministers from the 28 NATO nations gathered in Brussels, Stoltenberg also reiterated his call for Turkey and Russia to calm the crisis and to find ways to ensure there is no repeat.

"We will work on further measures to assure Turkey's security," Stoltenberg said at the start of the two-day meeting dominated by Syria, Ukraine and relations with a "more assertive" Russia, as well as future plans in Afghanistan.