She has become one of the Obama administration's most visible surrogates on health care, announcing the release of $851 million in federal financing for health clinics, calling for tougher nutritional standards in the government's school lunch program and urging Democrats to rally around the president's efforts to revamp health care. The high-profile emissary? Not Kathleen Sebelius, the health and human services secretary, or Nancy-Ann DeParle, the White House health policy adviser. It is Michelle Obama, the first lady. 'We're at a critical juncture in the debate about health care in this country,' Obama said at a clinic here in June. 'The current system is economically unsustainable, and I don't have to tell any of you that. And despite having the most expensive health care system in the world, we're not necessarily healthier for it.' After several months of focusing on her family, her garden and inspiring young people, Obama is venturing into more wonkish terrain. She is toughening her message and talking more openly about influencing public policy as she works to integrate her efforts more closely with those of policymakers in the West Wing. While her efforts are most visible in the health care arena, Obama is also focusing on other issues. In May, she convened a meeting -- with James L. Jones, the president's national security adviser; Gen. James E. Cartwright, the vice chairman of the Joint Chiefs of Staff; and Peter R. Orszag, the White House budget chief, among others -- to consider new policies and programs to help military families. But Obama, a Harvard-educated lawyer and former hospital executive, is still treading cautiously as she fleshes out her priorities: promoting healthy living and community service and supporting military and working families. Susan Sher, the first lady's new chief of staff, emphasized that Obama would not testify before Congress or argue the merits of competing health care plans. Obama's aides say she will promote policy, not make it. Jocelyn Frye, Obama's policy director, said the first lady wanted to 'draw the connection between this massive conversation that's happening about health reform and what's really happening to people on the ground.' Obama's advisers say this is a natural progression. After settling her family into the White House, the first lady could more easily turn to the garden and then a discussion of obesity, the importance of preventive care and corresponding government policies and legislation, they say. 