House Democrats will meet today to pass on to House Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.) their concerns about the direction in which their party is heading in revising the tax code.

The session was requested by members of the party's more liberal wing, who would prefer a tax bill that reduced the federal deficit and provided a smaller tax cut for upper-income taxpayers. The caucus is expected to be a fractious one: Rep. James Oberstar (D-Minn.) and others collected signatures from 100 legislators asking for the caucus.

"The purpose of the meeting is to open the process up more to members," Oberstar said. "The[Ways and Means] chairman has, understandably, had a closed process and asked us to keep our powder dry. By the time we finish keeping our powder dry, it will all blow away."

President Reagan, meanwhile, called on Congress to get moving on the tax-revision plan.

Speaking at the White House yesterday to a group of businessmen, lobbyists and trade association representatives, Reagan said "there can be no excuse" for delaying tax reform.

"To those who say that we can't get tax reform passed this year, I have a simple answer. The word I'd like to use was a favorite of Harry Truman's. And Bess didn't like it much," the president said to laughter. "And since I can't think of an acceptable substitute word . . . I'll just use more words and say, yes, it can be passed this year if all of us do what we know is the statesmanlike thing to do and quit playing political games."

Members of the Ways and Means Committee, meanwhile, spent another day going over Rostenkowski's proposed alternatives to Reagan's tax plan. The chairman has said he considers the options, which were developed by the committee staff, a starting point. Panel members said yesterday that, although they still believe they will produce a tax bill, it won't look much like the document now before them.

"We were kind of waiting for the staff options to bail us out," said Rep. Robert T. Matsui (D-Calif.). "Now, we've found out they were just a first step. Looking back, we should have realized the process would take more than two weeks." One likely change is the addition of a fourth bracket that would raise the top tax rate for individuals to 40 percent from the proposed 35 percent, Matsui said.

During their closed-door meeting, Ways and Means members objected to such specific staff proposals as eliminating the tax-exempt status of day care provided on the job, restricting depreciation deductions for new investments and curtailing, but not eliminating, the deduction for state and local taxes.

Such complaints -- like the objections expected to be voiced today in the caucus and those raised during a meeting of committee Democrats Monday -- actually may facilitate the process of revamping the tax code, some members suggested.

"What's wrong with a little catharsis?" asked Rep. Barbara B. Kennelly (D-Conn.). "This is a big thing we're trying to do. You have to have some plain talk."

Also yesterday, Treasury Secretary James A. Baker III sounded less than optimistic about the chances of producing a tax measure this year. He told a group of business executives that, if the House can not pass legislation by Nov. 1, "We may have to look into the first part of next year."

Rostenkowski is expected to tell Democrats that, if the committee does not produce a bill, Reagan will be able to accuse Democrats of blocking his domestic agenda -- and congressional Republicans will be able to avoid making the painful choices included in their own president's tax proposals. Already, Republicans on the Ways and Means Committee have been unable during several meetings in recent days to agree on a strategy to handle tax overhaul.