WASHINGTON (AP) — President Barack Obama plunges on his first day in office into the task of governing a nation he vows to change, calling together U.S. economic and military leaders Wednesday to address America's daunting challenges. A day after claiming his place in history as the first black U.S. president, he is faced with pulling the U.S. economy out of its nosedive even as he moves on his promise to withdraw American forces from Iraq while sending still more soldiers to America's other war in Afghanistan. After returning to the White House from a round of inaugural balls at about 1 a.m., Obama ventured into the Oval Office for the first time as president around 8:30 a.m., presidential spokesman Robert Gibbs said. In addition to meeting with his advisers, Obama welcomes public visitors into the White House, as Congress scrutinizes his economic revival plan and takes up the nominations of Hillary Rodham Clinton as secretary of state and Timothy Geithner for treasury secretary. A new poll underscored the sense of anticipation that accompanied Obama into office. The Associated Press-Knowledge Networks survey found that by a 3-1 margin, people feel more optimistic about the country's future now that Obama has been inaugurated, including 30 percent of Republicans. "Tonight, we celebrate. Tomorrow, the work begins ... Together, I am confident we will write the next great chapter in America's story," Obama declared Tuesday night at the Commander in Chief Ball, one of 10 official inaugural celebrations that kept him and first lady Michelle Obama up into the early morning hours. Obama's Democratic Party now controls both chambers of Congress and the White House for the first time since 1994, providing a chance for the new administration to succeed if he can work in concert effectively with lawmakers. The capstone to four days of inaugural festivities takes place at the Washington National Cathedral on Wednesday morning, with a national prayer service that is a tradition dating to the time of George Washington, the country's first president. Obama and his wife were to welcome hundreds of members of the public to a White House open house, part of his pledge to make government and those who govern more accessible for the governed. A meeting with his economic team was planned to assess his approach and plot the way forward. Taking over the White House with 11 million Americans out of work and trillions of dollars in stock market savings lost, Obama said that turning around the limping economy is his first and greatest priority. Congress already has given him a second installment of financial-industry bailout money, worth $350 billion, and is fast-tracking a massive economic stimulus bill of $825 billion or more. "Fortunately we've seen Congress immediately start working on the economic recovery package, getting that passed and putting people back to work," he said in an ABC News television interview. "That's going to be the thing we'll be most focused on." The breakdown of confidence in the country's banks, occurring on the same day as his inauguration, gave the matter fresh urgency. Financial stocks, many of them falling by double digit percentages, led a huge drop on Wall Street Tuesday that left the major indexes down more than 4 percent. The market's faith in the outgoing Bush administration's $700 billion bailout effort was already waning. Many experts believe Obama's administration will have little choice but to pump more money into the banking sector or create an entity to buy banks' soured assets such as subprime mortgages so they will start lending again. Addressing the war in Iraq that he has promised to end was featuring prominently in Obama's first day as well. According to officials, Obama will conduct a video teleconference late in the afternoon with members of the National Security Council as well as the U.S. military commanders in the two war zones. Obama has said he wants U.S. combat troops out of Iraq in 16 months, as long as doing so would not endanger either the Americans left behind for training and terrorism-fighting or the security gains in Iraq. He has said he would use that drawdown to bolster the U.S. presence in Afghanistan, where a resurgent Taliban has been gaining ground. Summoned to the White House to discuss the way ahead in the wars were Defense Secretary Robert Gates — the lone Republican Cabinet holdover from the Bush administration — along with chairman of the Joint Chiefs of Staff, Adm. Mike Mullen; the top military commander in the Middle East, Gen. David Petraeus, and other members of the security council. Participating from the war front were to be Gen. Ray Odierno, the top U.S. commander in Iraq, and Gen. David McKiernan, the top commander in Afghanistan, according to two senior military officers. The officials spoke on condition of anonymity because the meeting has not been officially announced by the White House. While Obama gets to work in earnest at the White House, Congress planned to do its part. A Senate committee was taking a close look at Obama's $825 billion economic revival package. On the other side of the Capitol, the House planned a vote on legislation setting conditions on Obama's use of the new infusion of $350 billion in financial bailout money. Getting the Obama administration fully staffed also was proceeding. Within hours of Obama's swearing in, the Senate approved six members of his Cabinet. His choice of Clinton to be secretary of state awaited a Senate vote Wednesday. Her confirmation was held up for a day by Republican John Cornyn of Texas who raised concern over the foundation fundraising of her husband, the former president. Also left unconfirmed was Geithner, the nominee to head the Treasury Department. He faces the Senate Finance Committee, also Wednesday, where he will have to explain his initial failure to pay payroll taxes he owed while working for the International Monetary Fund. The Senate Judiciary Committee could take up the question of Eric Holder for Obama's attorney general. The new president signaled that a flurry of executive actions, studied and prepared during his two-month-plus transition, should be expected soon. Among the possibilities for the first day was the naming of a Middle East envoy, critical at a time of renewed hostilities between Israelis and the Palestinians; an order closing the U.S. military prison at Guantanamo Bay, in Cuba, a move that will take considerable time to execute. The military on Tuesday suspended war crimes trials there pending a review. Also expected was a prohibition of the harsh interrogation techniques that have damaged the U.S. image worldwide. Beyond that, the new president could overturn the so-called Mexico City policy that forbids U.S. funding for family planning programs that offer abortion. Obama also was expected to lift President George W. Bush's limit on federal funding of embryonic stem cell research. But Gibbs said that most such substantive executive orders will probably wait until Thursday or later. The push on Wednesday will be to issue orders making clear Obama's intention to hold all White House staff to high ethics standards and to start delivering on the pledge of making his administration more transparent to Americans. ___ Associated Press writers Jennifer Loven, Lolita C. Baldor and Robert Burns contributed to this report.