Prime Minister Ibrahim al-Jaafari called on neighboring countries Thursday to help prevent foreign terrorists from crossing into Iraq as a series of attacks killed more than a dozen Iraqis and two American soldiers.

Al-Jaafari's appeal came a day after a top U.S. military official said the leaders of Iraq's most notorious terrorist group recently held a secret meeting in neighboring Syria, where they plotted the recent wave of insurgent violence that has killed hundreds of people.

"There are infiltrations of non-Iraqis through the border to carry out sabotage activities," al-Jaafari said of the meeting that may have been attended by most-wanted militant Abu Musab al-Zarqawi himself. "It's up to our geographical neighbors. We are keen to preserve relations between us and neighboring countries, and these relations should be good."

He was speaking after a meeting with U.S. Deputy Secretary of State Robert Zoellick, who said al-Zarqawi's aim was to divide Iraqi society.

"Part of these attacks stem from the successes of the new government. The insurgents wanted to stop the elections and failed. The insurgents wanted to stop the formation of a new Iraqi government and they failed, so now they are trying to split the society," Zoellick said.

He added that "it's very clear that this evil wants to destroy a democratic Iraq. These people will not be easy to counter because they commit suicide in a random way."

Zoellick said he and al-Jaafari had discussed the militant meeting in Syria and the prime minister "was quite strong in his statements about the need for Iraq's neighbors, and particularly Syria ... not to undermine stability here."

The Syrian meeting has led to one of the bloodiest periods since the U.S.-led invasion two years ago. More than 520 people have been killed - including an oil ministry employee gunned down in front of his house Thursday - since the country's new Shiite-dominated government was announced April 28.