"It's just an incorrect story. We have a lot of assets looking for Osama bin Laden," Mr. Bush said.
Mr. Bush vowed to keep hunting for the al Qaeda terror leader, a search that has been fruitless in the nearly five years since the Sept. 11 attacks.
"No ands, ifs or buts. My judgment is it's just a matter of time," he said. "We're not going to stop looking so long as I'm the president; not only for Osama bin Laden, but anybody else who plots and plans attacks against the United States of America. We're going to stay on the offense so long as I'm your president."
In a rare out-of-town news conference, Mr. Bush also said he wants to rally world support in confronting North Korea over its missile tests to send an unmistakable message to the leader of the communist regime.
"It's your choice, Kim Jong Il. You've got the choice to make," Mr. Bush said.
He also said anew that he would await a recommendation from Gen. George W. Casey, the top U.S. military commander in Iraq, on when to withdraw American forces.
"We will lose if we leave too early," Mr. Bush said. There are just under 130,000 U.S. troops in Iraq.
The president sought to explain why he was committed to seeking U.N. Security Council support on dealing with North Korea, whereas he launched the invasion of Iraq in 2003 after failing to obtain the council's support.
"All diplomatic options were exhausted as far as I was concerned" in confronting Iraqi leader Saddam Hussein, Mr. Bush said.
At the same time, he conceded that awaiting U.N. consensus, both on dealing with North Korea and Iran, was adding to delay.
"You know, the problem with diplomacy: It takes a while to get something done. If you're acting alone, you can move quickly," Mr. Bush said.
He said he wanted to make clear to the North Korean leader "with more than one voice" that the world condemned the test firing this week of seven missiles, including a long-range missile that failed.
Mr. Bush said the United States had "a reasonable chance" of shooting down the long-range missile, if it had not failed.
But he also said, "Our anti-ballistic systems are modest, they are new."
The United States has a rudimentary missile defense program in which interceptor missiles based in Alaska and California — linked to a network of satellites, radar, computers and command centers — are designed to strike and destroy incoming ballistic missiles.