BRUSSELS, June 16 (Reuters) -

The EU's second most senior diplomat affirmed the bloc's support for the nuclear deal between world powers with Iran, including via the use of a new payment system for barter-based trade designed to circumvent U.S. sanctions.

Helga Schmid, the secretary general of European Union external action service, visited Tehran on June 15. She helped negotiate the deal in 2015.

The status of the Joint Comprehensive Plan of Action (JCPOA) or Iran's nuclear agreement with world powers has been precarious since President Donald Trump pulled the United States out last year and toughened its sanctions regime against Tehran.

The European Union's foreign service said that, in Tehran, Schmid had reiterated the bloc's commitment to the deal, which has been "delivering on its primary goal ... to ensure that Iran does not acquire material or equipment to develop a nuclear weapon."

She had also discussed "EU efforts ... to enable the continuation of legitimate trade with Iran," including working to put into operation the Instex payment channel set up by France, Britain and Germany to facilitate non-dollar trade.