TALLINN, Estonia — President Bush said today that an al-Qaida plot to stoke cycles of sectarian revenge in Iraq is to blame for escalating bloodshed, and refused to debate whether the country has fallen into civil war.

"No question it's tough, no question about it," Bush said at a news conference with Estonian President Toomas Hendrik Ilves. "There's a lot of sectarian violence taking place, fomented in my opinion because of the attacks by al-Qaida causing people to seek reprisal."

Bush, who travels to Jordan later in the week for a high-stakes summit with Iraqi Prime Minister Nouri al-Maliki, said an uptick in violence does not represent a new era in Iraq. The country is reeling from the deadliest week of sectarian fighting since the war began in March 2003.

The president dated the current spike to the Feb. 22 bombing of a sacred Shiite shrine in Samarra, which triggered attacks and reprisal counterattacks between the Shiite majority and Sunni minority, and raised fears of civil war.

Bush said he will ask al-Maliki to explain his plan for quelling the violence.

"The Maliki government is going to have to deal with that violence and we want to help them do so," the president said. "It's in our interest that we succeed."

But Bush repeated his administration's reluctance to talk with Syria and Iran about their willingness to help stabalize Iraq.