WASHINGTON // When the US State Department issued a travel alert for Europe last Sunday, it came as little surprise here following a week of leaks about heightened risk assessments from intelligence sources and an apparently related record number of US drone attacks in Pakistan.
But among US allies abroad, the alert raised suspicions about Washington's true intentions, and Thursday a senior Pakistani diplomat suggested that the alert might have been raised for domestic US political reasons rather than as the result of solid intelligence.
Wajid Hassan, the Pakistani high commissioner to Britain, told The Guardian newspaper that he would not rule out that the alert had more to do with midterm US congressional elections because, he said, the United States had not supplied Pakistan with any "definite information about terrorists and al Qa'eda", and the driving force behind the alert was the White House.
Mr Hassan's comments must be seen in the context of extremely tense US-Pakistani relations.
But European intelligence officials and politicians have also expressed scepticism about the alert, not least in Germany, one of three countries believed to be a target of the alleged plots.
Most of the intelligence that led to the travel alert appears to have come from a single source, Ahmed Sidiqi, a German national of Afghan origin, captured in Pakistan in July. Mr Sidiqi, who US officials say received arms training by militant groups in Pakistan's tribal areas, is said to have provided US interrogators with what has been characterised as a "steady stream" of detailed information.
That is understood to include information about at least 10 people linked by a mosque in Hamburg that was once used by Mohamed Atta, the suspected ringleader of the 9/11 attacks in New York and Washington.
The men are suspected of planning to set up cells in Europe ready to engage in commando style-operations, described in both US and European media as similar to the 2008 Mumbai attacks. German intelligence officials have also had access to Mr Sidiqi and the information he has provided.
In spite of this, and although Germany raised alert levels for its nationals abroad, Berlin did not raise them at home. Britain and France, the other two countries believed to be targets of the alleged plots, did the same, indicating they did not take the information as seriously as the United States.
Indeed, last week, Thomas de Maizière, Germany's interior minister, said he saw no sign of an imminent attack on Germany and described the danger to Germany as merely "hypothetical". Single-source intelligence is generally considered highly unreliable. Yet, said Fred Burton, a senior intelligence analyst at Stratfor, a Texas-based global intelligence company and a former counterterrorism agent with the US State Department, single-source intelligence was often all that could be obtained.
"If you can get access to one of the operational players, they can be a treasure trove of data," he said.
The information gleaned from Mr Sidiqi will have been corroborated with other intelligence services, explaining the time frame from the capture of Mr Sidiqi to the issuing of the alert, Mr Burton said.
In all, Mr Burton said, the alert had been a "prudent" measure since there was a "perfect storm" of threats coinciding, all of which would have combined to create "a general angst that something could be afoot".
But the information was also not specific enough to have warranted a full-blown warning, which would have seen the US government advise its citizens against travel to Europe, Mr Burton acknowledged.
Moreover, the lack of arrests or arms caches uncovered in the wake of the Mr Sidiqi's capture also suggested an "unknown variable", he added.