The House of Delegates, bowing to members' pointed questions about Gov. Harry Hughes' agreement to let the banking conglomerate Citicorp open branches in Maryland next year, delayed a key vote on the controversial proposal today after approving a related bill that would let all outside banks into the state by 1989.

Supporters of the so-called "Citicorp bill," which enjoys the backing of Speaker Benjamin L. Cardin (D-Baltimore) and the House Economic Matters Committee, said they expect the House to approve it early next week.

In their first Saturday session marking the waning days of the 1985 General Assembly, several House members complained about the haste with which the legislature has been asked to approve Hughes' March 7 agreement with he giant New York bank.

"I didn't see these amendments until today," said Del. Gary R. Alexander (D-Prince George's), waving a copy of the complex document that would let Citicorp and other banks open branches in Maryland in mid-1986 if each banking company agrees to create at least 1,000 jobs and build a corporate facility in the state at a cost of at least $25 million.

Although the House delayed the Citicorp bill, it earlier gave preliminary approval in a voice vote to a related measure that would establish a four-year period when banks in Maryland, 12 southeastern states and the District of Columbia could open operations in the state before Maryland's borders would be opened to full interstate banking.

During those four years, banks such as Citicorp would not have the right to merge with or acquire Maryland banks or set up branch operations in the state. But the Citicorp bill would enable those institutions to set up branches in 1986 after fulfilling the jobs and capital construction requirements.

The Citicorp bill has been the object of a lobbying campaign that is intense even by Annapolis standards. The powerful Maryland Bankers Association, which in the past has contributed thousands of dollars to politicians' campaigns, opposes the Citicorp agreement as unfair to the 89 commercial banks in this state.

Watching the debate today from opposite galleries overlooking the ornate House chamber were William K. Weaver, the bankers' longtime lobbyist here, and Franklin Goldstein, an equally experienced advocate in Annapolis for Citicorp.

Lobbying over the Citicorp bill has not been limited to these two men. Three days ago, Hughes made only his second trip to the office Cardin has occupied as speaker since 1979 to press for House approval of the Citicorp bill.

"It was good, hard lobbying," said Cardin, who late this week reiterated his support for the legislation.

However, in an unusual move, Cardin and other House leaders did not even vote today on Alexander's motions to delay consideration of the Citicorp and regional-interstate banking bills.

Some House members said they believe Cardin's refusal to vote on the motions indicated his private ambivalence about the Citicorp measure. If the House does approve the bill, it will set that chamber on a collision course with the Senate, whose leaders have criticized the legislation as inconsistent with the pending regional-interstate banking law.

The Senate Finance Committee has scheduled a vote Monday on the interstate banking legislation. During debate in the House today, Economic Matters Chairman Frederick C. Rummage (D-Prince George's) alluded to the coming conflict with the Senate, saying, "They are not even going to consider a Citicorp bill."

In other action today, the House approved bills that would limit the investment of state pension funds in corporations doing business with South Africa and a so-called "death with dignity" measure allowing doctors to withdraw some medical procedures for terminally ill patients.

Earlier today, the House Constitutional and Administrative Law Committee voted 12 to 8 to restrict political action committees from making contributions totaling more than 20 percent of a candidate's campaign fund. Prospects for the bill are bleak, largely because the Senate has killed a bill to limit PAC contributions, several delegates said.