U.S. counterterrorism officials are increasingly concerned about the ambitions and fresh tactics of a Taliban commander suspected of instigating a ferocious attack on a police training school in Lahore, Pakistan, this week.

In the attack, followers of Pakistani Taliban leader Baitullah Mehsud—armed with guns and grenades—held off Pakistani security forces during eight hours of fighting. Initial reports said eight police and eight attackers were killed, though some reports predicted the final death toll would be considerably higher. In the days after the attack, Mehsud himself—or someone claiming to be him—claimed credit for the police-academy attack and also told The Associated Press and Pakistani media that his group was planning an attack on the White House in Washington. American officials don't take that threat seriously; they say that Mehsud and his group don't have the reach to launch attacks in the United States. 

But in a bulletin issued earlier this week to local cops around the country, the FBI took note of the apparent evolution in Mehsud's tactics involving the use of firearms. The bulletin also reported Mehsud's threat against the White House, but according to an official familiar with its content, did not invest the threat with particular credence. In an e-mailed statement, FBI spokesman Richard Kolko acknowledged: "The FBI is aware of the claims made by Baitullah Meshud. He has made similar threats to the U.S. in the past and we deem these new statements as aspirational ... A bulletin was sent to our law enforcement partners for situational awareness." The FBI statement added: "We are not aware of any imminent or specific threats to the U.S." In a purported interview with The Associated Press (U.S. officials say it is conceivable the militant being interviewed was not really who he claimed to be), Mehsud, an increasingly prominent leader of Taliban forces based in Pakistan's tribal areas who was recently reported to have pledged loyalty to fugitive Afghan Taliban leader Mullah Omar, directly threatened the Executive Mansion. "Soon we will launch an attack in Washington that will amaze everyone in the world," Mehsud told the AP reporter, though he provided no further details of the supposed attack plan. (Article continued below...)

U.S. officials believe that Mesud's claim of responsibility for the Lahore police-academy attack is considerably more credible than his threat to attack Washington. According to three U.S. counterterrorism officials, who asked for anonymity when discussing sensitive information, historically Mehsud, who is reported to be based in the tribal area of South Waziristan, has never operated, or previously demonstrated much interest in conducting terrorist operations, outside Pakistan.

One remote contingency that American officials leave open is the possibility that Mehsud, who experts believe historically has had contacts with hard-core Al Qaeda operatives hiding out in the same rough area where Mehsud's forces hold sway, picked up word that other militants based in the neighborhood have launched a plot against the White House. However, two U.S. officials familiar with current intelligence reporting agreed with the FBI assessment that there is no specific or credible information available at present indicating that such a conspiracy is currently afoot inside the United States.

The attack on the police academy near Lahore is the latest in a series of operations attributed to Mehsud inside Pakistan, most or all of which appear to be aimed at undermining the authority of the country's shaky government and security forces. Other recent attacks attributed to him or his followers include a suicide car bombing of a group of soldiers and another suicide attack on a police station in Islamabad, Pakistan's capital. Both U.S. and Pakistani officials have also linked Mehsud to the December 2007 assassination of Benazir Bhutto, the former Pakistani prime minister and wife of Pakistan's current president, Asif Ali Zardari. 

According to reports from the region, a group with links to Mehsud's Taliban faction also has been claiming responsibility for an attack earlier this month on a convoy carrying Sri Lanka's national cricket team to a match in Lahore. During that operation, half a dozen policemen and a bus driver were killed, but the attackers escaped. Late last year, a group of Islamic militants armed with grenades and handguns staged a spectacular attack against hotels and other civilian targets in Mumbai, the financial capital of India. After initially rejecting Indian investigators' claims that the attackers were from Pakistan, Pakistani authorities later conceded the plot was hatched from their country. So far no direct links are publicly known to have surfaced between the Mumbai attackers, believed to be affiliated with a Kashmir-oriented jihadist group called Lashkar-e-Taiba, and Mehsud or his Taliban crew.

One murky question facing U.S. and local authorities when evaluating threats, real or imagined, from Mehsud and other militants based in Pakistan is whether they are still getting support from elements of Pakistan's own intelligence service, known as the ISI. For years, U.S. authorities have pressured their Pakistani contacts over suspicions that elements of ISI—particularly a division within the sprawling agency known as "S Wing"—not only helped to set up Islamic militant groups like the Taliban and Lashkar in the days when the West saw them as a bulwark against Soviet expansionism, but have continued to provide the jihadists with clandestine support into the present.