The retired general who served as George Bush's special envoy to deal with the Kurdistan Workers' party (PKK) today said the US has failed to keep its promises to Turkey to confront the Kurdish group

Retired air force General Joseph Ralston declined to say why he stepped down several weeks ago. But published reports have said that he was frustrated by the Bush administration's failure to act against the PKK.

He said Turkey may feel that it has no choice but to attack the PKK in northern Iraq.

In his first extended comments since his departure, Gen Ralston told McClatchy Newspapers the US is unwittingly "driving, strategically, the Turks and the Iranians together" because both nations share concerns about Kurdish separatist groups.

"The US government should make good on the commitments they have made to the Turks," Gen Ralston said.

The White House and the US military are wary about opening a new front in the war in Iraq - particularly in generally stable northern Iraq - by launching assaults against the PKK.

Neither the US-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, Major General Benjamin Nixon, last week said he planned to do "absolutely nothing" to curb PKK activities.

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

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