ECB chief Mario Draghi said "an ample degree of monetary stimulus remains necessary", as inflation has yet to show signs of a sustained upward trend. Earlier in the week, U.S. President Donald Trump polled Republicans on whether they would prefer Stanford University economist John Taylor or Fed Governor Jerome Powell for the job. Prices recovered from the early session weakness to post a strong gain, boosted by comments from Saudi Arabia's Crown Prince backing the extension of OPEC-led production cuts.