INDIANOLA, Iowa - Former Alaska Gov. Sarah Palin assailed corporate favouritism in a campaign-style speech to tea party activists in early-voting Iowa Saturday, as the clock winds down on her decision to enter the presidential campaign.

The 2008 Republican vice-presidential nominee did not say whether she planned to seek the 2012 presidential nomination. She has imposed a late-September deadline for announcing her plans.

Her closely watched appearance in Iowa, which leads off the nominating contests with its early February caucuses, and plans to headline a tea party rally Monday in New Hampshire, home of the leadoff primary, elevated the sense of urgency surrounding her.

Time may be running out for Palin to command the spotlight as she has throughout the summer, despite her coyness about a candidacy. There are three nationally televised debates for the declared Republican candidates, which are expected to shape the race in a way that could leave the popular conservative figure behind.

Speculation about Palin's plans, stoked again last month by a trip to Iowa, are at an all-time high.

Although she has drawn large crowds, she has done none of the political spadework other presidential contenders have such as meeting with key party activists and officials.

Meanwhile, Republican candidates who are also popular with the small government, anti-tax tea party movement, including Texas Gov. Rick Perry and Minnesota Rep. Michele Bachmann, have emerged as contenders for the nomination.

And while Palin also remains popular with tea party activists, her popularity with rank-and-file Republicans has dropped sharply.

In her Iowa speech Saturday, Palin laid the rhetorical groundwork for an outsider campaign by advocating proposals aimed at addressing the nation's stubbornly high unemployment.

She proposed expanded and less-regulated oil drilling, pared down business regulations and eliminating the corporate income tax, all points aimed at addressing the top issue in Republican polls.

"It's not just fear of a double-dip recession, and it's not the shame of a credit downgrade," she said. "This is a systemic crisis due to failed policies and incompetent leadership."

She set herself apart from President Barack Obama, a Democrat seeking re-election, and, in a veiled way, from some declared Republican presidential candidates.

"This is why we must remember the challenge is not simply to replace Obama in 2012. The real change is who and what we will replace him with," Palin told the tea party rally in a rural area south of Des Moines. "Folks, you know it's not enough to change the uniform."

The audience of about 2,000 supporters from all over the country, dampened by heavy rains that quit shortly before the midday speech, erupted into chants of "Run, Sarah, Run!"

But Palin gave no response, and steered clear of any reference to a candidacy, even in jest as she has in the past, during her 40-minute speech.

"It would be a tremendous disappointment to a lot of people if she didn't run," said Mike Archambault, who travelled from Oregon to attend the rally.

Palin touted her two years as Alaska governor as an example of confronting powerful interests including the state's oil industry. She accused Obama and leaders in Washington, D.C., of coddling corporations, at heavy cost to the taxpayers.

And while not naming any of her would-be rivals for the party nomination, she also said other Republicans were guilty of repaying campaign donations with policy perks.

In recent weeks, media reports have pointed out instances in which people who have donated to Texas Gov. Rick Perry's campaigns have later received appointments.

That has left Perry vulnerable to criticism of corporate influence.

"There is a name for this. It's corporate, crony capitalism," she said.

Asked later if she was referring to Perry, she said all Republican candidates should be on alert.

"I want all of our GOP candidates to take the opportunity to kill corporate capitalism that is leading to this cronyism that's destroying our economy," Palin said, while in a crush of hundreds of supporters asking for autographs and posing for pictures.

Palin also said it was not a campaign speech.

"It was a thank-you-tea-party-Americans speech," she told reporters.