WASHINGTON — As they prepare to take control of Congress this week and face up to campaign pledges to restore bipartisanship and openness, Democrats are planning largely to sideline Republicans from the first burst of lawmaking.

House Democrats intend to pass a raft of popular measures as part of their well-publicized plan for the first 100 hours, including tightening ethics rules for lawmakers, raising the minimum wage, allowing more research on stem cells, and cutting interest rates on student loans.

But instead of allowing Republicans to participate fully in deliberations, as promised after the November 7 Democratic victory, Democrats now say they will use House rules to prevent the opposition from offering alternative measures, assuring speedy passage of the bills and allowing the Democrats to trumpet early victories.

Rep. Nancy Pelosi, a Democrat of California who will become House speaker, and Rep. Steny Hoyer, a Democrat of Maryland who will become the majority leader, finalized the strategy in a flurry of conference calls and meetings with other party leaders during the holiday recess. A few Democrats, worried that the party would be criticized for reneging on an important pledge, argued unsuccessfully that they should grant the Republicans greater latitude when the Congress convenes on Thursday.

The episode illustrates the dilemma facing the new party in power. The Democrats must demonstrate that they can break legislative gridlock and govern after 12 years in the minority, while honoring their pledge to make the 110th Congress a civil era in which Democrats and Republicans work together to solve the nation’s problems. Yet in attempting to pass laws key to their prospects for winning re-election and expanding their majority, the Democrats may have to resort to some of the same hard-fisted tactics used by the Republicans for the past several years.

Democratic leaders say they are torn between giving Republicans a say in legislation and shutting them out to prevent them from derailing Democratic bills.

“There is a going to be a tension there,” Rep. Christopher Van Hollen, a Democrat of Maryland, said. Mr. Van Hollen is the new chairman of the Democratic Congressional Campaign Committee. “My sense is there’s going to be a testing period to gauge to what extent the Republicans want to join us in a constructive effort or whether they intend to be disruptive.”

House Republicans have begun to complain that Democrats are backing away from their promise to work cooperatively. They are working on their own strategy for the first 100 hours, and part of it is built on the idea that they might be able to break the Democrats’ slender majority by wooing away some conservative Democrats.

The Democrats intend to introduce their first bills within hours of taking the oath of office on Thursday. The first legislation will focus on the behavior of lawmakers, banning travel on corporate jets and gifts from lobbyists, and requiring lawmakers to attach their names to special spending directives and to certify that such earmarks would not financially benefit the lawmaker or the lawmaker’s spouse. That bill is aimed at bringing legislative transparency that Democrats said was lacking under Republican rule.

Democratic leaders said they are not going to allow Republican input into the ethics package and other early legislation because several of the bills have already been debated and dissected, including the proposal to raise the minimum wage, which passed the House Appropriations Committee in the 109th Congress, a spokesman for Ms. Pelosi, Brendan Daly, said.

For clues about how the Democrats will operate, the spotlight is on the House, where the new 16-seat majority will hold power over the way the chamber operates. Most of the early legislative action is expected to stem from the House.

“It’s in the nature of the House of Representatives for the majority party to be dominant and control the agenda and limit as much as possible the influence of the minority,” a political scientist at Rutgers University, Ross Baker, said. “It’s almost counter to the essence of the place for the majority and minority to share responsibility for legislation.”

In the Senate, by contrast, the Democrats will have less control over business because of their razor-thin 51-to-49-seat margin and the fact that individual senators wield substantial power. Senate Democrats will allow Republicans to make amendments to all their initiatives, starting with the first measure — ethics and lobbying reform, James Manley, who is a spokesman for Senator Reid of Nevada said.