WASHINGTON — Faced with a military buildup in Iraq that could drag into next year, Pentagon officials are struggling to choose Army units to stay in Iraq and Afghanistan longer or go there earlier than planned.

Military officials acknowledge that units scheduled to come home this summer — such as the Hawai'i-based 3rd Brigade, 25th Infantry Division — could be forced to extend their tours by up to 120 days to maintain the Baghdad security buildup.

Five years of war have made fresh troops harder to find but Pentagon officials are trying to identify enough units to keep up to 20 brigade combat teams in Iraq. A brigade usually has about 3,500 troops.

More than 7,000 Schofield Barracks soldiers with the division headquarters, 3rd Brigade Combat Team and the Combat Aviation Brigade left Hawai'i in July and August for a year-long deployment to northern Iraq. Several thousand are part of the 3rd brigade, which is headquartered out of Kirkuk Air Base.

Lt. Col. Drew Meyerowich, the Hawai'i-based battalion commander for about 1,000 U.S. troops near Kirkuk — most of whom are with the 2nd Battalion, 27th Infantry under the 3rd brigade — attempted to squelch rumors of an extension in a Feb. 7 letter to families back home as his unit passed the halfway mark on the deployment.

"I have discussed these rumors with every member of the team and continue to tell them to worry about the next six months and not worry about a single day past that," Meyerowich said in his letter. "There is no truth to the rumor that we are being extended at this time. I have been briefed that some units in Iraq may be extended, but we are not currently one of them."

In 2004, about 5,500 Isle troops had their combat tours in Iraq extended two months.

Final decisions — which have not yet been made — would come as Congress is considering ways to force President Bush to wind down the war, despite his vow that he would veto such legislation.

In the freshest indication of the relentless demands for troops in Iraq, Maj. Gen. Benjamin R. Mixon, commander of coalition forces in the north, told reporters Friday that his troops have picked up the pace of their attacks on the enemy in Diyala province, northeast of Baghdad.

"Could I use more forces? No question about it," Mixon said, adding that he had asked for more.

The top U.S. military commander in Iraq, Gen. David Petraeus, said a day earlier that it was likely that additional U.S. forces will be shifted to areas outside the capital where militants are regrouping, including Diyala. The region has become an increasingly important staging ground for militant groups, including al-Qaida in Iraq.

"There have been about 30 percent more offensive actions and attacks. Many of those are initiated by us; some are initiated by them," Petraeus said from a military base outside of Tikrit. "I am cautiously optimistic that in the next 30 to 60 days that we're going to see some significant differences in the security situation in Diyala."

If not, he said, he'll go back and ask for still more support.

Petraeus has said that the U.S. buildup in Iraq would need to be sustained "for some time well beyond the summer" to garner the needed results.

JUGGLING SCHEDULES

Maintaining increased troop levels, said military officials, will require troops to return for what could be their second or third tours in Iraq or Afghanistan, and force military leaders to juggle the schedules to give soldiers a full 12 months at home before returning to battle.

The officials would speak only on condition of anonymity, because no final decisions have been made and no formal requests for the forces have come from commanders in Iraq.

But they said it is beginning to appear likely that Petraeus will ask to maintain much of the buildup at least through the end of the year, and possibly into 2008.

One official said planners are scrambling to figure out what combination of units and schedules can be fashioned that could give Petraeus what he wants and have the least negative impact on the troops.

The complex scheduling must identify which units would have been home for 12 months and be trained and ready to go, plus whether the needed equipment would be available and what impact a schedule change has on other plans for the equipment or troops months down the road.

TRAINING FOR RETURN

Combat troops, meanwhile, are coming to realize that the Pentagon can't fulfill its commitment to give soldiers two years at home for every year they spend deployed.

At Fort Drum, N.Y., the 1st Brigade of the 10th Mountain Division is already training for a return to Iraq this summer. The brigade, which spent a year in Iraq and got home last summer, is not yet on any official list of units scheduled to deploy, but it's likely to go in late summer.

"It's prudent planning for us to be prepared to go back in a year," said Fort Drum spokesman Ben Abel.

Initially, the Bush plan called for sending 21,500 extra U.S. combat troops to Iraq — mainly to Baghdad — with the last of five brigades arriving by June. So far two of the brigades have arrived in Iraq. The latest estimates indicate that up to 7,000 support troops may also be needed, including more than 2,000 military police.