Partisan differences over health care continued to sharpen Monday as Senate Finance ranking member Chuck Grassley (R-Iowa) signed on to a GOP letter urging President Barack Obama oppose a public plan.Sen. Orrin Hatch (R-Utah) spearheaded the letter, which was signed by Republican members of the Finance Committee, the panel in charge of writing health care legislation in the Senate. But as the top GOP Senator on the committee, Grassleys signature is notable because he has been a champion thus far of the bipartisan negotiations led by Chairman Max Baucus (D-Mont.).One of the more divisive issues in the health care reform debate is the creation of a brand new public health insurance option. In a letter dated June 2, 2009, you specifically endorsed the creation of such a public health insurance option, the letter reads.At a time when major government programs like Medicare and Medicaid are already on a path to fiscal insolvency, creating a brand new government program will not only worsen our long term financial outlook but also negatively impact American families who enjoy the private coverage of their choice, the letter continues.In a letter to Baucus and Senate Health, Education, Labor and Pensions Chairman Edward Kennedy (D-Mass.) last week, Obama said the implementation of a government-run, public insurance option to compete with private insurers is among his top priorities for any health care reform.Most Republicans are vehemently opposed.