By James Coomarasamy
BBC News, Washington
US officials have been making two main and, in some ways, contradictory points about the arrest of seven men in Miami for allegedly hatching a terror plot.
The first is an upbeat one: the alleged plot to blow up the Sears Tower in Chicago and the FBI building in Miami was not far advanced at all, they say.
The Miami group were apparently targeting Chicago's Sears Tower
In the words of one official, the alleged terrorists were aspirational, rather than operational.
But their second point - made forcefully by the US Attorney General Alberto Gonzalez and the FBI director Robert Mueller - is a rather more frightening one: Americans must be aware of the heightened possibility of home-grown terror plots, of threats that can come from their own streets.
According to the indictment against them, the Miami group may have been inspired by al-Qaeda and may have thought they were in contact with an al-Qaeda operative, who turned out to be an undercover agent.
But they were not part of a sleeper cell, sent from a foreign country. They were, in the main, US citizens, who had allegedly developed a hatred for their own country.
Over the past year, the US authorities claim, they have disrupted three separate cases of home-grown terrorism.
One of those involved two men from Atlanta, who have since been linked to the arrests of 17 others in Toronto earlier this month in connection with an alleged plot to attack public buildings and behead the country's prime minister.
It is this case which has really provoked anguish in the US, prompting concerns about security along the border with Canada, and reflection on the possibility that Americans - inspired, perhaps, by extremist teachings - could carry out the sort of deadly attacks that were seen in London and Madrid.
The FBI building in Miami was also on the alleged target list
It will be chilling for Americans to hear that, according to this latest indictment, the seven arrested men were boasting of an attack that would have been bigger than 9/11.
At the same time, there is, at this stage, plenty of uncertainty about the Miami arrests.
The families of the men, aged between 22 and 32, are loudly proclaiming their innocence.
Others are wondering how serious they could really have been if, as the indictment suggests, they were relying on their supposed al-Qaeda contact to supply them with boots.
Clearly, though, the FBI believes its undercover agent gathered enough evidence, over a period of months, to justify the arrests.
Whether or not the arrests result in convictions, it is hard to avoid the conclusion that there is a political dimension to the way they have been presented.
The attorney general has faced a lot of criticism about the government's methods of tracking terrorists after 9/11.
Those methods include the so-called warrantless wire tapping programme, and the newly-disclosed policy of monitoring the supposedly confidential bank transactions of tens, maybe hundreds of thousands of Americans.
The group of men arrested lived inside a warehouse in Miami
Any breakthrough in the fight against terrorism can only bolster the government's defence of these kinds of programmes.
Yet there is also a potential downside for the Bush administration in talking up the threat of domestic terror.
One of the arguments made for the continued presence of US troops in Iraq is that it is better to fight terrorists abroad than to fight them at home.
If the US is having to do both, surely the public will begin to call this argument into question?