Liberal House Democrats, alarmed by the apparent progress the Reagan administration is making on securing additional funding for the MX missile, have stepped up efforts to rally opposition to the nuclear weapon.

Several MX critics attending a weekend conference for House Democrats said they hope to meet with House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) to press for strong leadership efforts to defeat the MX in a vote expected later this month.

These same Democrats have increased pressure on House Armed Services Committee Chairman Les Aspin (D-Wis.) to reverse his past support for the missile. Aspin, who was crucial to previous administration efforts to get the MX approved, said he has not decided how to vote this time.

But several House Democrats said they believed that he had pledged during his recent campaign for Armed Services chairman to oppose the MX -- provided arms talks with the Soviet Union were under way.

During the weekend retreat at the Greenbrier resort, Aspin said, he was confronted by Rep. Howard E. Wolpe (D-Mich.), who demanded to know how Aspin was going to vote. Aspin denied having made any commitments on the MX to win the chairmanship.

MX supporters have said that they think that they have enough votes to obtain further funding for the missile and that the opening of the arms talks on March 12 in Geneva is likely to help their cause.

Congress last year approved $1.5 billion for 21 MX missiles but froze funding through last Friday, at which point President Reagan could request that the funds be released. The administration has indicated that it will do so, and the issue is expected to come up for a vote shortly after the arms talks begin.

The Democrats were here for a weekend retreat organized by the House Democratic Caucus. Organizers called the event a success.

Majority Leader James C. Wright Jr. (D-Tex.) said House leaders would begin circulating budget options in the next two weeks in seeking a Democratic consensus on that issue.

The focus of today's sessions was practical politics. Rep. Tony Coelho (D-Calif.), chairman of the Democratic Congressional Campaign Committee, told his colleagues they must begin to act now to counter GOP efforts to capture state legislatures in time for the post-1990 reapportionment fight.

Former Reagan White House communications director David R. Gergen, in the only session of the weekend open to the news media, said Reagan and the Republicans have gained political success by sticking to a few simple messages. His Democratic audience expressed frustration that Reagan has escaped blame for the big budget deficits.

Several Democrats said they were upset with the Saturday speech by Chrysler Corp. Chairman Lee A. Iacocca, in which he pleaded for action to prevent Japanese industry from swamping American markets.

"I thought it was racist," said Rep. Robert T. Matsui (D-Calif.). "He said the Japanese are going to come in the back yard and used words like 'Sayonara.' He was raising the specter of yellow peril."

Wright said that he told Iacocca of the complaints and that Iacocca had not intended to offend anyone.

Iacocca could not be reached for comment.