BRUSSELS (Reuters) - UK and EU negotiators made some, but not decisive, progress on Sunday on the three most thorny issues barring a new trade deal, a senior EU diplomat said on Monday. The diplomat spoke under condition of anonymity as the negotiators - EU’s Michel Barnier and UK’s David Frost - were pushing to close the gaps on Monday with just 24 days before Britain leaves the bloc’s single market and customs union. “Barnier and Frost negotiated intensively... and made some progress but not quite managed to bridge differences,” said the person. “There has been no decisive progress though some progress has been made.” The person named “robust and enforceable cooperation on state aid non-regression clause” and “stable access to UK waters” for EU fishing vessels as the outstanding issues. “We are at the make-it-or-break-it moment,” they said.