Baghdad, Iraq ? The scale and sophistication of militant attacks in Iraq are steadily increasing, with coordinated strikes and complicated ambushes that increasingly hit their targets, officials and analysts said Wednesday.

The spike in bloodshed — more than 200 dead in four days — has stifled American hopes that the transfer of sovereignty and the prospect of a democratic vote in four months could take the steam out of the uprising and pave the way for a reduction in U.S. troops.

Instead, there are signs the Americans and their Iraqi allies are facing an enemy more determined than ever. Insurgents have learned from past mistakes and shifted strategy, cooperating more closely with each other and devising new ways to put their relatively simple arsenal to treacherous use.

“More thought is going into the execution of the attacks,” said Lt. Col. Paul Hastings of Task Force Olympia, which is trying to bring stability to a swath of northeastern Iraq.

Militants now follow up roadside bomb attacks with a deluge of rocket-propelled grenades instead of fleeing, or fire off mortar rounds to lure soldiers out of their base and into freshly laid mine fields, military commanders say.

In a July attack in Samarra, for example, militants detonated a car bomb and then hammered a military headquarters with a mortar barrage as troops fled the building. Five American soldiers died.

At least 47 people were killed Tuesday in a car bombing in Baghdad targeting would-be police recruits, the deadliest single strike in the capital in six months.

“The enemy has been able to construct IEDs (Improvised Explosive Devices) that are more complex, include more rounds in the form of a ‘daisy chain,’ and tend to have a higher lethality,” said Maj. Neal O’Brien of the Army’s 1st Infantry Division.

O’Brien also said that an increase in the use of car bombs in the past two months coincided with an influx of foreign fighters with the bomb-making know-how in July.

An Iraqi police officer calls for help after a car bomb explosion in central Baghdad, Iraq. Tuesday's attack targeting police recruits killed at least 59 people.

Groups join forces

On Sunday, militants in Baghdad struck the U.S.-guarded Green Zone — the seat of the Iraqi government and the U.S. Embassy — with their biggest mortar and rocket barrage to date, many of them showing signs of careful aim.

Hours later, guerrillas used a car bomb to disable a U.S. patrol on a main Baghdad thoroughfare before detonating a second car bomb that wrecked a Bradley fighting vehicle sent to assist the patrol. They then opened fire on the wounded crewmen as they fled the vehicle.

“The set of attacks that occurred over the weekend were definitely more simultaneous than in the past,” said Lt. Col. Steven Boylan, spokesman for coalition forces in Baghdad.

Analysts say the plethora of armed groups behind the insurgency increasingly are working together.

“As time goes on, various gangs get together and it does become more coordinated,” said Judith Kipper, a Middle East expert at the U.S.-based Council on Foreign Relations. “Groups start small, get know-how and become more lethal over time.”

American commanders, however, insist the stepped-up attacks and the possibility of increased cooperation among militant groups are signs that the insurgents have realized time is running out for them with the onset of elections in January.

“There is a level of desperation associated with the anti-Iraqi forces, they absolutely don’t want to see free elections and reconstruction projects work,” Hastings said.

Security challenge

But the attacks have fueled a growing backlash against the United States and interim Iraqi Prime Minster Ayad Allawi.

“The situation is getting worse day after day and the American are still in the streets,” said Kawakib Butris, 40, a supermarket worker in Baghdad. “This government didn’t ensure the simplest things to us like security, electricity and other services.”

In response to the growing violence, the Bush administration announced plans this week to divert about $3.5 billion in Iraq reconstruction funds for security.

NATO, however, moved close to an agreement on sending hundreds of military instructors to Iraq, with France and the United States narrowing their differences Wednesday over the mission to run a training center for the country’s new armed forces.

The plan will likely entail the deployment of 200 to 300 NATO instructors to Iraq and would complement a much larger U.S.-led operation to build new Iraqi armed forces, which are expected to total 260,000.

Iraqi police and national guardsmen have been the focus of many of the recent attacks, creating a challenge for the United States and Allawi as they strive to strengthen the Iraqi security forces.