With Americans prepared to vote in congressional elections on Tuesday, Obama said authorities had uncovered a "credible terrorist threat" against the United States in the discovery of two breadbox-sized packages in Dubai and Britain that apparently contained explosive material.
Speaking at the White House, Obama said a top aide had spoken to Yemen's president, Ali Abdullah Saleh, and that Saleh had pledged full cooperation in the investigation. He said Yemen-based al Qaeda in the Arabian Peninsula has been plotting to attack the United States.
"Going forward, we will continue to strengthen our cooperation with the Yemeni government and to disrupt plotting by al Qaeda in the Arabian Peninsula, and to destroy this al Qaeda affiliate," Obama said.
Al Qaeda in the Arabian Peninsula, an arm of al Qaeda thought to include Yemenis and Saudis, has stepped up attacks on Yemeni and Western targets since it claimed responsibility for a failed U.S. airliner bomber in December.
Friday's events came as Obama prepared to embark on a weekend of campaign travel on behalf of Democratic candidates, including a Saturday night stay in Chicago.
White House spokesman Robert Gibbs said at this point the travel plans were unaffected by the plot.
Obama pledged U.S. officials will spare no effort to find the source of the packages and any additional plots. He said U.S. security would be increased for air travel in response to the incident for as long as it takes.
RAPID RESPONSE
Obama spoke publicly about the incident the day after the plot was uncovered in a bid to show that he and his administration were on top of the situation. He was heavily criticized for taking three days to make his first public statement after the failed bomb attempt on an U.S. airliner last Christmas Day.
Gibbs did not directly answer a question about whether Obama was addressing the issue forcefully in order to look tough on national security in hopes of boosting his Democrats' chances in Tuesday's congressional elections.
The White House released a photograph of Obama being briefed in the Situation Room by intelligence and counterterrorism officials.
Obama's homeland security adviser, John Brennan, would not say how the United States learned of the plot.
"We were on to this. We were looking for packages that were of concern," he told reporters.
Of the plotters, Brennan said: "Clearly they are looking to identify vulnerabilities in our system and take advantage of those vulnerable ... We've been able to stay ahead of them."
He said it was unclear how the devices were supposed to be activated.
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