A debate is under way within the US government about whether to kill an American citizen and suspected member of al-Qaeda who is believed to be planning attacks on US targets overseas.
The case underscores the complexities of Barack Obama's new stricter targeting guidelines for the use of deadly drones.
The CIA drones watching the suspect cannot strike because he is an American citizen. The Pentagon drones that could are barred from the country where he is hiding, and the Justice Department has not yet finished building a case against him.
Four US officials said the suspected terrorist was in a country that refused US military action on its soil. Obama's new policy says American suspected terrorists overseas can be killed only by the military, not the CIA.
Two of the officials said the man was an al-Qaeda facilitator directly responsible for deadly attacks against US citizens overseas and who continued to plan attacks against them using improvised explosive devices.
The officials said the suspected terrorist was well-guarded and in a fairly remote location, so any unilateral attempt by US troops to capture him would be risky and even more politically explosive than a US missile strike.
White House press secretary Jay Carney said on Monday that he would not comment on specific operations and pointed to Obama's comments in his major counter-terrorism speech last May about drone policy.
"When a US citizen goes abroad to wage war against America and is actively plotting to kill US citizens, and when neither the United States, nor our partners are in a position to capture him before he carries out a plot, his citizenship should no more serve as a shield than a sniper shooting down on an innocent crowd should be protected from a SWAT team," Carney said, quoting from Obama's speech last year.
Under Obama's new guidelines, lethal force must be used only "to prevent or stop attacks against US persons, and even then, only when capture is not feasible and no other reasonable alternatives exist to address the threat effectively".
The target must also pose "a continuing, imminent threat to US persons" - the legal definition of catching someone in the act of plotting a lethal attack.