US Secretary of State Hillary Clinton signed an agreement with Greece on Sunday aimed at clamping down on the import and sale of stolen archaeological artefacts. Under the new agreement, the import of protected archaeological artefacts will be illegal if they have not first been cleared by the Greek authorities. Clinton signed the agreement with Greek Foreign Minister Stavros Lambrinidis at a ceremony in the Acropolis museum in Athens, which itself is a UNESCO World Heritage Site and home to the iconic Parthenon. It was the 15th such agreement the US has signed with other countries, and Clinton said the system worked. \"America is just as committed to Greece\'s future as we are to preserving your past,\" she said. Greek Culture Minister Pavlos Yeroulanos welcomed the agreement. \"There is still a lot of traffic, a lot of thefts in general going on,\" he said. This kind of accord was the best way to tackle the problem, he added. During earlier talks with Lambrinidis, Clinton discussed Greece\'s struggle to tackle the debt crisis that has engulfed it -- and is threatening to engulf the eurozone as a whole.