US President George W Bush cautioned on Saturday that the threat from a plot to detonate liquid explosives on commercial flights may not have passed.
He also denied Democratic charges that he was trying to use the crisis for political gains in an election year.
"We believe that this week's arrests have significantly disrupted the threat," Bush said in his weekly radio address. "Yet we cannot be sure that the threat has been eliminated."
British authorities arrested two dozen suspects on Thursday for allegedly plotting to use liquid explosives to blow up airliners flying from Britain to the United States.
The arrests prompted the United States to raise its terror alert to the highest level ever and prompted airports to ban passengers from taking liquids, gels and creams on planes.
Bush, who returns to Washington on Sunday after a 10-day working vacation at his ranch, urged air travellers to be patient with the stricter security measures. "The inconveniences you will face are for your protection and they will give us time to adjust our screening procedures to meet the current threat," he said.
Democrats on Friday accused Vice President Dick Cheney of trying to use this week's arrests in Britain to Republican advantage in November Congressional elections, which will determine whether Democrats or Republicans control the US Congress.
Cheney said on Wednesday the Democrats' defeat of Connecticut Democratic Senators. Joe Lieberman in the state's primary on Tuesday because of his support of the Iraq war could embolden "Al-Qaeda types."
Senate Democratic leader Harry Reid, Nevada said,"Once again, GOP (Republican) leaders are using terrorism and our national security as a political wedge issue. It is disgusting -- but not surprising."
Bush said the suspected plot in Britain "reminds us of a hard fact: The terrorists have to succeed only once to achieve their goal of mass murder, while we have to succeed every time to stop them."
"Unfortunately, some have suggested recently that the terrorist threat is being used for partisan political advantage. We can have legitimate disagreements about the best way to fight the terrorists, yet there should be no disagreement about the dangers we face," he said.
Democrats in their weekly radio address charged Bush has short-changed domestic security needs and the war on terror, and they blamed him for bungling the Iraq war.
Senator Mark Pryor, Arkansas, said the administration's "poor management" in Iraq "has created a rallying cry for international terrorists" and "diverted our focus, our military and more than $300 billion from the war on terrorism."
Pryor said US ports, borders and chemical plants remain unsecured, emergency personnel lack critical resources and the military, including the National Guard, was stretched.
"It's time for Washington to be tough and smart about the threats we face," he said. "Americans deserve real security, not just leaders who talk tough but fail to deliver."