MEXICO CITY, Feb 18 (Reuters) - The Mexican government will inject up to $1.6 billion into state oil company Petroleos Mexicanos (Pemex) this year and offer a tax break of 75 billion Mexican pesos ($3.68 billion), a senior official with direct knowledge of the matter told Reuters on Thursday. The world’s most indebted oil company, Pemex had more than $110 billion in financial debt at the end of the third quarter last year while its liabilities far exceeded its assets. (Reporting by Ana Isabel Martinez; Writing by Stefanie Eschenbacher; Editing by Chizu Nomiyama)