Public diplomacy chief Karen Hughes has pledged to deepen U.S. cooperation with key NATO ally Turkey. Ms. Hughes was speaking on the final stop of a Mideast tour aimed at boosting America's image in the Islamic world.

Karen Hughes during a meeting in Ankara with Turkish Foreign Minister Abdullah Gul

Speaking to reporters after meeting in Ankara with Turkish Foreign Minister Abdullah Gul, Ms. Hughes said the United States faces, what she termed, "a huge public diplomacy challenge." The way to overcome that challenge she said is for America to work in partnership with Turkey.

Ms. Hughes also acknowledged that the United States needs to help Turkey deal with a resurgent terrorist campaign launched by separatist rebels of the outlawed Kurdistan Workers Party, known as the PKK.

Turkey has been urging the United States to take military action against about 5,000 PKK fighters dug into the mountains of Kurdish controlled northern Iraq.

Karen Hughes talks with Turkey's Chief Rabbi Isak Haleva before meeting with religious leaders at Topkapi Palace in Istanbul

Differences over the PKK reflect broader policy disputes between Turkey and the United States over Iraq. Turkey remains suspicious of the federal model embraced by Iraq's draft constitution, fearing that it could lead to the dismemberment of its southern neighbor along ethnic lines.

Turkey is especially concerned that U.S. support for its Iraqi Kurdish allies will result in the emergence of an independent Kurdish state on its borders. An independent Kurdistan could in turn become a magnet for Turkey's own restive Kurdish population.

Anti-American sentiment has been on the rise in Turkey since the U.S.-led occupation of Iraq. A recent opinion poll showed that only 17 percent of Turks support America's war on terror. Many believe the war targets Muslims. Novels about U.S. forces occupying Turkey continue to dominate the bestseller lists.

Relations between the two NATO allies suffered a big blow in 2003 when Turkey's parliament, responding to popular sentiment, voted against a bill that would have enabled U.S. troops to use Turkey to invade Iraq from the north.

Turkish officials now express concern that the United States will seek Turkey's help in isolating neighboring Iran and Syria.

Even so, officials on both sides have taken steps to improve ties in recent months. Turkey's Prime Minister, Recep Tayyip Erdogan, has spoken repeatedly of the strategic importance of relations with the United States.

Earlier this week, National Security Advisor Steve Hadley traveled to Ankara where he met with Turkish President Ahmet Necdet Sezer and Mr. Erdogan.

But analysts say that unless the United States takes firm action against the PKK, relations between the two countries will remain vulnerable.