WASHINGTON--President Reagan asked Congress yesterday for the final installment in a $100 million aid package for Nicaragua's Contra rebels, while House Democrats sought to drive home the point that past aid money remains unaccounted for.

The President, one day after saying in a major speech that the Iranian initiative was a mistake, declared it was time to move on to other matters.

Vice President George Bush said he was "catching the dickens" from some people fornot stopping the Iran initiative but declared theadministration would not be judged in the long runon "the agony of the Iran affair."

On the subject of U.S. aid for the Contras,Reagan sent Congress a certification that there is"no reasonable prospect" of peaceful settlementand a democratic Nicaragua unless the aid iscontinued. The certification automaticallytriggers $40 million in additional aid unlessCongress disapproves it within 15 days.

The Democratic proposal, on the other hand,would shut off aid to the rebels until previousaid is accounted for, including any money divertedfrom Iranian arms sales or solicited from privatesources.

"We as a party need to make a statement on thisissue," said Rep. David Bonior (D-Mich). However,he said aid opponents probably do not have thevotes to override an almost certain presidentialveto of their action, which is expected to pass inthe House but faces a less certain future in theSenate.

The Democrats' move was seen as primarily aneffort to focus attention on the administration'sinability to account for more than 10 milliondollars in previous aid money, an issue alreadyraised by last week's Tower commission report onthe Iran-Contra affair as well as by congressionalinvestigators.

In his certification to Congress, Reagan saidthat "continued intransigence by Nicaragua hasprevented progress."

"U.S. support for regional negotiationshas...continued throughout the period," thePresident said, but "there is no reasonableprospect at this time that the government ofNicaragua will engage in a serious dialogue withrepresentatives of all elements of the Nicaraguandemocratic opposition, accompanied by a ceasefireand an effective end to the existing constraintson political freedoms."

Bush Response

Speaking to a Republican group in Davenport,Iowa, Bush said trading arms for hostages "wasn'tso hot" an idea. "I wish I'd seen the signals" asReagan's Iran policy went awry, he said.

He added that although he was not prominentlymentioned in the Tower commission report, whichwas critical of Reagan's management style, "I'mcatching the dickens" for failing to stop theinitiative