Rebels fire artillery in the latest attempt to take a vital military base near the southern city of Deraa.<br /> <br />The fighters are attempting to reverse recent regime gains in the south of the country.<br /> <br />Speaking in the Russian town of Sochi, UN Chief Ban Ki-moon urged countries to remain focused on finding a political solution to the crisis, criticizing Syrian authorities for not allowing UN inspectors to investigate claims of chemical weapons use.<br /> <br />(SOUNDBITE) (English) UN SECRETARY-GENERAL, BAN KI-MOON, SAYING:<br /> <br />"Our team, is ready at any time. Within 24 to 48 hours notice, they can immediately conduct an investigation. I again urge the Syrian authorities to be flexible and allow our teams to have an on-site investigation."<br /> <br />Syrian rebels complain that government forces are benefiting from Russian arms supplies, but Lavrov stressed Russia was merely honouring existing contracts.<br /> <br />(SOUNDBITE) (Russian) RUSSIAN FOREIGN MINISTER, SERGEI LAVROV, SAYING:<br /> <br />"We
