WASHINGTON — President Barack Obama's ambitious plans will face immediate political difficulty in a wary — and often parochial — Congress that's long resisted such fast, radical change.

It's not only lawmakers who tend to resist overturning the status quo. An army of lobbyists, grassroots interests, campaign contributors and others who make up insider Washington await, all eager to express their views on why Obama's plans need to be amended, if not defeated.

"He's going to get it from all sides," said Maya MacGuineas, president of the Committee for a Responsible Federal Budget, a Washington budget watchdog group.

Obama effectively said "bring it on" in his Saturday address on radio and the Internet.�

"The system we have now might work for the powerful and well-connected interests that have run Washington for far too long.�But I don't. I work for the American people," the president said. "I know these steps won't sit well with the special interests and lobbyists who are invested in the old way of doing business, and I know they're gearing up for a fight.�My message to them is this: So am I."

Some of Obama's troubles are purely political. All 435 seats in the House of Representatives as well as 36 Senate seats are up for election in 2010, and most lawmakers want something tangible to take home, such as money for a highway or a new school, rather than promises to cut the federal deficit in half four years from now.

The president, however, must also navigate a legislative system that seems almost unfathomable, a Congress where it often takes weeks just to set up a hearing, let alone rewrite big chunks of the nation's tax code. And even if they're inclined to act, many lawmakers are reluctant to tear up policies and programs to start from scratch.

For instance, Obama this week emphasized again that he wants to end earmarks, or the local projects that lawmakers routinely insert into spending bills without having them scrutinized by the normal legislative process. Earmarks are controversial because they sometimes are favors for special interests and other times seem extravagantly wasteful, such as the infamous "bridge to nowhere" in Alaska. Ending them would be a symbolic gesture showing that Congress and the White House are ready to make sacrifices to pare the budget.

Next week, however, the Senate plans to debate and vote on a $410 billion fiscal 2009 budget plan that currently contains about 9,000 earmarks costing $3.8 billion. The House of Representatives passed the bill Wednesday.

Even Obama's staunchest allies argued vociferously for the earmarks.

"We are a separate branch of government, and since we've been a country, we have had the obligation as a Congress to help direct spending," said Senate Majority Leader Harry Reid, D-Nev. "We cannot let spending be done by a bunch of nameless, faceless bureaucrats buried in this town someplace to take care of the needs of the states of Nevada, Washington and New York."

Much tougher tasks await. Lawmakers have been battling over environmental, health and tax policy for decades, and a seasoned array of powerful interests is again ready to pounce on Obama's sweeping proposals and bend them to their will.

One key element of Obama's budget calls for transforming health care, for example. Whenever such proposals are taken up, however, "all the icons come out — 'it's government intervention, it's too expensive' — it raises a lot of hackles," said Brian Bethune, chief U.S. financial economist at IHS Global Insight, a Lexington, Mass., economic research firm.