Baghdad ? U.S. military deaths plunged in May to the lowest monthly level in more than four years and civilian casualties were down sharply, too, as Iraqi forces assumed the lead in offensives in three cities and a truce with Shiite extremists took hold.

But many Iraqis as well as U.S. officials and private security analysts are uncertain whether the current lull signals a long-term trend or is simply a breathing spell like so many others before.

U.S. commanders also warn the relative peace is fragile because no lasting political agreements have been reached among the Shiite, Sunni and Kurdish communities.

Talks on returning Sunnis to the government broke down this week, and tensions among rival Shiite parties remain high despite a May 11 truce that ended weeks of bloody fighting in Baghdad’s Sadr City district.

Iraqis have experienced lulls in the past – notably after the January 2005 elections – only to see violence flare again.

“The security situation is much better than in the past three or four months, and I am making more money now,” said Falih Radhi, who runs a food store in eastern Baghdad. “Despite this, I have a feeling that this positive situation won’t last long and that violence may come back again.”

Nevertheless, the figures for May are encouraging, especially coming as the United States continues withdrawing the nearly 30,000 reinforcements that President Bush sent to Iraq early last year to curb the wave of Shiite-Sunni slaughter.

All five of the “surge brigades” rushed to Iraq last year will be gone by July, lowering the troop strength to about 140,000, U.S. officials say. There are currently about 155,000 U.S. troops in Iraq.

At least 21 American troopers were killed in May – four in non-hostile incidents. That’s one more than the lowest monthly figure of the war set in February 2004.

Meanwhile, Iraqi deaths were down, too.

At least 532 Iraqi civilians and security troopers were killed during the month, according to figures compiled by The Associated Press from Iraqi police and military reports. That’s down sharply from April’s figure of 1,080 and the lowest monthly total this year, according to the AP count.

It includes 10 people who were killed Saturday when a suicide bomber blew himself up at a police checkpoint in Hit.

Last Sunday, military spokesman Rear Adm. Patrick Driscoll said the number of attacks in the previous week fell to a level “not seen since March 2004,” although he did not give specific figures.

At the same time, Iraqi forces have taken the lead in offensives against the Sunni extremist al-Qaida in Iraq in the northern city of Mosul and against Shiite militiamen in Baghdad and Basra in the south.

U.S. and coalition forces assumed a support role in the three offensives, enabling them to avoid higher casualties which would have been expected had they been doing all the fighting.

With the trends looking positive, the top American commander in Iraq, Gen. David Petraeus, said in Washington last week that he is likely to recommend further troop cuts in Iraq but won’t promise more details until fall – as the U.S. presidential election campaign is approaching its climax.

But U.S. officials and private security analysts warn against rapid withdrawals and optimistic forecasts.

Former Pentagon analyst Anthony Cordesman wrote this week that despite some improvements among Iraqi forces, both Iraqi and U.S. officials continue “to sharply exaggerate the real-world readiness” of the country’s army and police.

Petraeus himself said it’s unlikely that Iraqi security forces can take the lead in all 18 provinces this year, as was recently predicted by the Pentagon.

“The overall trend in Iraq is positive, but we should be skeptical about overly optimistic assessments that we’ve ‘turned the corner’ in Iraq,” said Eric Rosenbach of the Belfer Center for Science and International Affairs and a former staffer of the Senate Select Committee on Intelligence.

“It’s more appropriate to say that we have a long road ahead of us rather than we’ve turned the corner.”

The reason for such caution is that many of the issues that contributed to the Iraq conflict remain unresolved – notably how the various ethnic and religious groups will share power.

Last August, the largest Sunni Arab political bloc pulled out of Prime Minister Nouri al-Maliki’s Cabinet, complaining it wasn’t getting enough say in decision-making. Talks on a Sunni return broke down this week.