MADRID - Underlying inflation in the euro zone is proving sticky and the European Central Bank is less optimistic about its trajectory than about overall price pressures, ECB Vice President Luis de Guindos said on Wednesday.

"We believe core inflation provides a better signal of medium-term inflationary trends," de Guindos said in Madrid. "Headline inflation will continue to decelerate but on core inflation we are not so optimistic."

(Reporting by Emma Pinedo Gonzalez and Jesus Aguado; writing by Balazs Koranyi; editing by John Stonestreet)