WASHINGTON — Beneath the resounding Democratic victories of the past two weeks, tensions have been growing between the House speaker, Rep. Nancy Pelosi, and many new committee chairmen and other members over her aggressive management style and her approach to the war, according to lawmakers and advisers.

Powerful committee chairmen have bridled at the California Democrat’s decision to impose six-year term limits on them. Liberal Democrats say she is being too cautious in confronting President Bush on the war in Iraq. Rank-and-file Democrats say she erred in denying Republicans more say in the early legislation, making the speaker appear autocratic.

And many Democrats complain that Ms. Pelosi is relying too heavily on a coterie of liberal allies from her home state and Massachusetts to the exclusion of more conservative lawmakers from the Midwest and the South.

The friction will present a growing challenge as Democrats move from the poll-tested, popular items that breezed through the House this month to more difficult legislative ventures, such as efforts to stem global warming, overhaul the nation’s immigration laws, shrink the budget deficit, and resolve the war in Iraq. It could hand Republicans a powerful political weapon as they seek to regain power in 2008 by challenging the crop of new Democrats hailing from Republican-leaning districts.

Rep. Marcy Kaptur, a Democrat of Ohio, praised Ms. Pelosi for guiding through so many popular legislative items so quickly but pleaded for her to develop a more inclusive leadership style.

“If I had any advice, it would be: ‘Don’t isolate yourself inside the territory you’re most familiar with,'” Mr. Kaptur said last week. Ms. Pelosi’s aides and allies say she is doing her best to be inclusive and to consult with the strongwilled old bull chairmen but that she must also make room for the new voices that helped the Democrats win back the majority. They said that although that will not be easy, most Democrats will be patient as the new majority settles in.