BAGHDAD, Iraq – Military force alone is "not sufficient" to end the violence in Iraq and political talks must eventually include some militant groups now opposing the U.S.-backed government, the new commander of U.S. forces in Iraq said Thursday.
"This is critical," U.S. Gen. David Petraeus said in his first news conference since taking over command last month. He noted that such political negotiations "will determine in the long run the success of this effort."
American troops have stepped up efforts to clear and secure major highways around the capital as part of the Baghdad security crackdown, which began last month. The Pentagon has pledged 17,500 combat troops for the capital.
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Petraeus said Thursday "it was very likely" that additional U.S. forces will be sent to areas outside the capital where militant groups are regrouping, including the Diyala province northeast of Baghdad.
The region has become an increasingly important staging ground for groups including al-Qaida in Iraq. Meanwhile, many Sunni extremists apparently have shifted to Diyala to escape the Baghdad clampdown.
Petraeus declined to predict the size of the expected Diyala reinforcements.
One of Iraq's most expansive militias — the Mahdi Army of radical Shiite cleric Muqtada al-Sadr — appears to have set aside its weapons under intense government pressure to lend support to the Baghdad security plan.
Mahdi militiamen also have allowed Iraqi authorities to try to protect at least 1 million pilgrims heading to Karbala, about 50 miles south of Baghdad.
Many are making the traditional trek on foot for rituals beginning Friday to mark the end of a 40-day mourning period for Imam Hussein, grandson of the Prophet Muhammad. Hussein's death in a 7th-century battle near Karbala cemented the schism between Sunnis and Shiites.
The processions have proved to be vulnerable targets, with attacks killing more than 170 people this week.
Al-Sadr issued a statement urging pilgrims to join in chants denouncing the attackers. "I ask almighty God to protect you from the sectarian sedition," said the message.
Petraeus denounced the "thugs with no soul" who have targeted Shiite pilgrims. "We share the horror" of witnessing the suicide bombings and shootings, he said.
He said U.S. forces are ready to help provide additional security for the pilgrims if asked by Iraqi authorities.
"It is an enormous task to protect all of them and there is a point at which if someone is willing to blow up himself ... the problem becomes very, very difficult indeed," he said.
Security forces in Karbala have taken unprecedented measures, including checkpoints for top-to-bottom searches and a six-ring cordon around the two main Shiite shrines. At least 10,000 policemen have been placed on round-the-clock patrols.
"All the city's entrances have been secured, and I call upon the pilgrims to follow the instructions of the security forces and let them do the necessary searches," Iraq's minister of state for national security, Sherwan al-Waili, said in Karbala.
In Baghdad, a mortar attack shattered some windows at the Iraqi Airways office on the airport compound, but the shells landed hundreds of yards from the passenger terminal and caused no serious flight disruptions.
Such attacks, however, send chills through Iraqi officials preparing to host an international conference Saturday on ways to help rebuild and stabilize the country.
The meeting will bring Iran and the United States to the same table for the first time in more than two years. Washington cut diplomatic ties with Tehran after the takeover of the U.S. Embassy by radicals in the wake the 1979 Islamic Revolution.
The United States has accused Iran of backing anti-American Shiite militants in Iraq, has detained Iranian officials there and has angered Tehran by beefing up its military presence in the Persian Gulf. Washington is also pushing for new sanctions on Iran over its nuclear program.
Iranian Foreign Minister Manouchehr Mottaki said Wednesday that his country hoped "the conference will bring forward the end of the presence of foreign forces" in Iraq — reiterating Tehran's stance that U.S. troops should withdraw.
Complete coverage is available in FOXNews.com's Iraq Center.