MOSCOW (Reuters) - Senior Russian officials held talks in Damascus on Monday with President Bashar al Assad, as the Syrian leader grapples with a crumbling economy that threatens to undermine military successes he has achieved with Moscow’s help in a decade-long conflict.

Russian Deputy Prime Minister Yuri Borisov and Foreign Minister Sergei Lavrov arrived after Moscow said it would support Damascus in the face of tougher U.S. sanctions, which penalise foreign firms dealing with Syrian government entities.

Syrian state media reported the meeting with Assad.

Officials from Syria and Russia, whose military support since 2015 helped Damascus reverse gains by Islamists and other rebels, have said the two sides plan to boost trade ties and will review energy, mining and power projects.

“Russia turned the tide for Assad and with the regime now facing its gravest challenges, Moscow is in a better position than any other time to further squeeze Assad,” said one Western diplomat who follows Syria.

Although Assad has now regained most of the territory he lost, the economy is in tatters, leaving many Syrians in poverty as the currency has lost 80% of its value.

Russia has criticised the new U.S. sanctions that took effect in June under the so-called Caesar Act. Washington says the sanctions aim to cut off revenue for Assad’s government and him push him back into U.N.-led talks to end the conflict.

Syria is pinning its hopes on Russia, its biggest foreign ally, to help it shore up its economy. Syria’s main regional ally, Iran, is itself also struggling to cope under a separate round of U.S. sanctions.

Hussam Taleb, a Syrian pro-government analyst, told Syrian state television the Russian visit would anger Washington which he said was “fighting us in our livelihood by passing the Caesar Act to deprive us of our wealth.”

Western diplomats say Russian President Vladimir Putin’s military involvement in Syria, its biggest Middle East intervention in decades, secured Moscow major regional influence and a bigger foothold in a naval base in Syria’s Tartus port.