President Barack Obama speaks about health care reform Monday at Arcadia University in Glenside, Pa.

Washington ? The White House is mounting a stinging, sustained broadside against health insurance rate increases as President Barack Obama and his aides enter what they hope will be the final stretch of a yearlong political war over health care reform.

Obama and Health and Human Services Secretary Kathleen Sebelius staged a two-pronged attack Monday in a stern letter to health insurance chief executives and a speech in which the president castigated insurance companies 22 times. “How much higher do premiums have to rise,” he demanded, “before we do something about it?”

The messages are part of a strategy that Obama and those around him have begun to employ lately, to ratchet up the pace and the populist appeal of their rhetoric against the health insurance industry. The barbed tone moves far beyond that of the 2008 presidential campaign, when Obama began to say that medical coverage should be accessible and affordable for more Americans.

It remains unclear whether the strategy, coming this late in the debate, will mobilize support among the public and on Capitol Hill for the legislation that the White House and congressional Democrats favor. Obama has asked Congress to conduct final votes on the proposal within 10 days, before lawmakers leave for a two-week break. Democratic congressional leaders, especially those in the House, are struggling to secure enough votes within their party; Republicans are calling for the proposal to be abandoned, saying that most Americans oppose it.

The near-daily demonization of the insurance industry is an attempt by the White House to play to Americans’ anxieties about the health care system — and about the prospect of changing it.

Polls consistently show that most people fear that the legislation would make their treatment more expensive. By focusing on escalating insurance rates, especially for the sliver of the market in which people buy health coverage individually, the administration is emphasizing that costs will increase if Congress does not act.

“Part of the motivating factor here is letting members of Congress know there’s a price to pay for failure,” White House Chief of Staff Rahm Emanuel said Monday in an interview. “And for the public, it’s important to remind them that there are premium increases of 40 percent for as far as you can see if nothing is done.”

Emanuel’s figure referred to a recent move by Anthem Blue Cross of California to raise premiums by 39 percent for people who buy individual policies.

Republicans doubt that the rhetoric will work. Linda DiVall, a GOP strategist, said White House officials “are trying to disguise their vulnerability” that the Democrats’ approach would not control costs “by hiding behind a greater villain” — insurance firms.

Last year, premiums for employer-sponsored health insurance rose by an average of 5 percent, while overall prices fell nearly 1 percent, according to the Henry J. Kaiser Family Foundation, a nonpartisan health policy and research organization. Over the previous decade, premiums went up by 131 percent, compared with 28 percent for inflation. The administration contends that the rate increases reflect excessive profits; insurance lobbyists counter that their rates simply mirror underlying increases in prices charged by doctors, hospitals and drug firms.

America’s Health Insurance Plans, the industry’s main lobby, plans to spend more than $1 million on a nationwide advertising campaign this week to, as one official with the group said, “set the record straight about rising health care costs.”

Americans’ attitudes toward health insurance are complex. Broad majorities of insured people say they are satisfied with their coverage, according to Washington Post-ABC News polls. Only one in eight say insurance would improve if the health care system were changed.

But that relative satisfaction coexists with anxiety. More detailed Kaiser surveys show that two-thirds of insured people say they worry that their insurance or their care will become more expensive — and nearly half say they have delayed or skipped care because of the cost.