More: The White House and the U.S. military have appeared leery about opening a new front in the war in Iraq — particularly in generally stable northern Iraq — by launching assaults against the PKK. Neither the U.S.-backed Iraqi government nor the semiautonomous Kurdish Regional Government has shown any inclination to go after the group.

The officer who commands U.S. forces in northern Iraq, Maj. Gen. Benjamin Nixon, last week said he planned to do "absolutely nothing" to curb PKK activities.

Ralston, a vice chairman of the Washington-based Cohen Group, a consulting firm, said the statement was "directly opposite" promises Bush has made to Turkey.

Asked whether the Turkish military would invade northern Iraq, which PKK fighters use to launch attacks into Turkey, Ralston said: "They're going to have to, in the absence of the U.S. doing anything."