WASHINGTON — Mayor Giuliani is returning to Iowa this week for the first time since his campaign announced that he would skip the August straw poll there, a move that angered party leaders.

Mr. Giuliani will deliver a speech Wednesday in Des Moines in which he may lay out the first substantive details behind the “12 commitments” that he has made the centerpiece of his presidential campaign. The former mayor announced the commitments last week in New Hampshire, and his aides have said he plans to expand on them in a series of speeches this summer.

Using Iowa as the backdrop for his initial policy address could help re-establish his presence in the state where the first presidential ballots are cast next year. His campaign would not comment yesterday on the subject of the Wednesday speech.

When Mr. Giuliani decided earlier this month that he would not participate in the traditional straw poll in Ames, his aides sought to emphasize that he remained committed to competing in the caucus in January.

Since then, the campaign has moved aggressively to back up that pledge, including the announcement of a state leadership team and opening a headquarters in Des Moines. He has also agreed to take part in a GOP debate the week before the straw poll in August.

In another sign that he is not writing off Iowa, Mr. Giuliani is dispatching several top advisors to the state for the entire week, to build support and bolster the campaign’s grassroots organization.

But even that simply may be a matter of playing catch-up to his top rivals, Mitt Romney and Senator McCain of Arizona, who have established much larger organizations in the state and spent considerably more time there in recent months.

Mr. Giuliani has focused more on the bigger states that have moved up their primaries and where his more liberal views on social issues should be less of a liability. Indeed, after giving his speech in Iowa on Wednesday, Mr. Giuliani is headed for two days in Florida, where he has already made several trips.

By contrast, the man who has jumped into the lead in recent state polls, Mr. Romney, spent the entire weekend traveling across the state. The former Massachusetts governor is the only leading GOP candidate to commit to the August straw poll, giving him a considerable advantage heading into the caucus five months later. Mr. Romney led Mr. McCain by 12 points and Mr. Giuliani by 13 points in a Des Moines Register poll taken last month, before the latter two candidates dropped out of the straw poll. Other polls have shown a closer race, and the likely entry of a former Tennessee senator, Fred Thompson, could further shake up the campaign.

The state GOP, which is officially neutral in the race, criticized both Messrs. Giuliani and McCain for opting out of Ames poll, which takes place at a fund-raiser for the party. At the time, a party statement said Mr. Giuliani was “not taking Iowans seriously” and described his campaign’s effort in the state as “lackluster.”

Mr. Giuliani’s aides have said the decision was made to conserve resources for the caucuses, and they acknowledged that the condensed primary calendar, involving larger, more expensive contests, had also played a role. Mr. McCain followed Mr. Giuliani out within hours, saying the event would no longer be a measurable test of campaign strength without one of the leading candidates participating.

A party spokeswoman, Mary Tiffany, said yesterday that Mr. Giuliani’s decision on the straw poll had not hurt his relationship with the state GOP, which will send a representative to his speech Wednesday. She said, however, that he has more work to do. “He clearly needs to keep showing his commitment,” Ms. Tiffany said. “He needs to keep coming here.”

As for whether he can do enough to win the caucus, she said, “Time will tell.”

The Giuliani campaign has not announced when the former mayor will return to the state after his speech on Wednesday; a spokeswoman, Maria Comella, yesterday would say only that he intended to come back “frequently.”