WASHINGTON — The White House and the country's top economic policymakers are still trying to perfect the right tonic — of bracing words and actions — to get the country safely through an unnerving credit crisis that has rocked Wall Street.

Their latest efforts came yesterday with President Bush and Treasury Secretary Henry Paulson using words to try to calm nervous investors. The Federal Reserve, meanwhile, took action — plowing $3.75 billion into the financial system.

Still, Wall Street experienced another erratic session. The Dow Jones industrials lost 30.49 points, while broader market indexes were slightly higher. Investors waiting for the Fed's next move made few big commitments to stocks.

Wrapping up a summit in Montebello, Quebec, with the prime minister of Canada and the Mexico's president, Bush said the U.S. economy remains in good shape and should be able to weather the financial storm.

"The fundamentals of the U.S. economy are strong," Bush said. "The fundamental question, 'Is there enough liquidity in our system?' And the answer is 'Yes, there is,' " the president declared.

Paulson also tried to strike a reassuring tone.

"We're going to work through this problem just fine," Paulson said in an interview with CNBC. He urged patience as investors reassess their appetite for risk, saying: "There's not going to be a quick solution" to some of the problems. "I think what the American people need to understand, these things take a while to play out."

Paulson, meanwhile, said the administration is concerned about soaring foreclosures and late payments, especially among people with spotty credit histories, and is exploring ways to deal with the problem.

"We're really focused on the subprime market, and we're really focused on the homeowners — mortgage holders — who are in danger of losing their homes," Paulson said.

After a five-year boom, the housing market turned to bust last year. And the combination of higher interest rates and weaker home values have clobbered homeowners, especially those with higher-risk subprime mortgages. Mounting defaults have forced some lenders out of business. Credit problems have spread to other borrowers. Nervous lenders have tightened standards, making it harder for individuals and companies to obtain credit — the lifeblood of the economy.

Increasingly restrictive lending conditions can crimp people's ability to buy big-ticket goods, such as homes, cars and appliances, and it can chill businesses' capital investment and hiring. Such a scenario would slow overall economic growth.

Paulson acknowledged the turmoil "will in all likelihood ... take a toll out of economic growth" but predicted the economy would still make its way safely through the troubles.

Trying to further stabilize wobbly markets, the Federal Reserve yesterday pumped another $3.75 billion into the financial system. It was the latest in a series of cash transfusions that have topped more than $100 billion in recent weeks. That's aimed at helping banks and other institutions get over the hump and carry out their business more smoothly.

In another move yesterday, the Fed cut the fee bond dealers pay to borrow Treasury securities from the central bank. It was temporarily lowered from 1 percent to 0.5 percent.