Politics or Security?

This article at MSNBC says that the terrorist suspects arrested the day after Lieberman lost his primary did not have plane tickets and that in fact no attack was iminent. This is not to say they weren't bad guys; they were. The British had been watching some of them for years and wanted to continue surveillance for another week or more.

But the United States pressured to arrest them immediately.

Why would US officials do that if there is no imminent threat? Some of the arrested blokes did not even have passports, apparently. Wouldn't it be better to watch them a little longer, hoping to get more information and evidence, maybe have them give up some other conspirators or contacts?

Instead, the US pushed Britain to make the arrests the day after Lieberman's loss.

This is the way our government makes us more secure? Decide the timing of significant arrests based on political rather than security concerns?