By George Georgiopoulos and Michele Kambas ATHENS (Reuters) - Greece's leftwing government expressed confidence on Tuesday that parliament would approve a debt deal with lenders, despite an angry reaction from some of its own lawmakers who accused it of caving in to pressure for more austerity. Concessions offered by Prime Minister Alexis Tsipras, including hikes to tax and pension contributions, garnered a cautious welcome from euro zone leaders but triggered a furious reaction from some leftists in the ruling Syriza party. Deputy parliament speaker and Syriza lawmaker Alexis Mitropoulos said the concessions were "not in line with the principles of the left" and would cause "social carnage".