Markets set to rise at Friday's open as investors decide if patch of economic disappointments is past.

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NEW YORK (CNNMoney.com) -- U.S. stocks were poised to advance at the start of Friday's open, although trading could be volatile amid anxiety about the economy.

At 7:01 a.m. ET, Dow Jones industrial average, S&P 500 and Nasdaq 100 futures were higher.

Futures measure current index values against perceived future performance and offer an indication of how markets may open when trading begins in New York.

Blue-chip stocks have pulled back for three days straight amid concerns about the economy. Wall Street tumbled Thursday after Standard & Poor's cut its outlook for the United Kingdom to "negative" from "stable," spurring worries that a similar downgrade could happen to the United States.

Those concerns pushed the dollar to its lowest level in five months against a basket of currencies on Friday.

Ken Wattret, economist for BNP Paribas in London, said the markets seem to be stuttering after rallying over the last few weeks. He said that stocks need some "better news on the economy" and some "positive surprises" to drive them forward.

"It's a bit difficult to sustain gains onward unless the macroeconomic news can sustain it," said Wattret. "My feeling is that the economic news is going to be a bit more patchy going forward. But that doesn't mean that we can't end the week on a bright note."

One other influence on trading Friday: It's the start of the Memorial Day weekend. U.S. markets will be closed Monday for the observance.

Autos: The U.S. government said Thursday it invested an additional $7.5 billion in GMAC, the main source of financing for General Motors (GM, Fortune 500) customers and the main lender for Chrysler.

0:00 /4:26AIG could not fail
Companies: AIG (AIG, Fortune 500) chief Edward Liddy announced late Thursday that he plans to depart the company once the insurer's board of directors finds a replacement.

A consortium of private equity firms acquired BankUnited FSB in Florida after the savings and loan was shut down by federal regulators Thursday. BankUnited was the 34th bank to fail so far this year, and the largest.

World markets: Stocks in Asia finished the session in negative territory, dragged lower by economic worries. Major markets in Europe posted modest gains in midday trading.

Money and oil: The dollar continued to fall against major international currencies, including the euro, yen and British pound. Oil prices gained 43 cents a barrel to $61.48.