PRAGUE, DEC. 18 -- Czechoslovakia's new leader, Milos Jakes, committed himself today to the Communist Party's long-standing conservative political line as a key meeting of the party's Central Committee failed to take decisive action on even a modest economic reform package.

The opening events in Jakes' tenure, following the retirement of party chief Gustav Husak yesterday, suggested there would be little immediate change in the policies of this East European nation, which has been slow and apparently reluctant to follow the initiatives of Soviet leader Mikhail Gorbachev.

In his first speech to the Central Committee, Jakes pledged to pursue a modest "restructuring" of the economy launched by Husak earlier this year and said he would work to "increase citizens' rights and freedom."

At the same time, he strongly praised Husak and his policies and aggressively attacked "the right-wing opportunists and revisionists" of the 1968 communist government of Alexander Dubcek, whose "Prague Spring" reforms prompted a Soviet-led invasion.

"There is no doubt that today our opponents would like to bring about a retreat from fundamental principles of socialism," the 65-year-old party chief declared in the speech, published in the state press today. "They will not live to see that. We took a lesson from 1968-69 and know where such a retreat leads."

Western observers said Jakes' statement, which echoed the hard-line rhetoric of Husak's 18-year rule, was in keeping with the new leader's background as an orthodox loyalist who oversaw -- and, by some accounts, led -- purges of hundreds of thousands of reform-oriented party members in the aftermath of the 1968 invasion.

At the same time, the aggressive affirmation of the official view of 1968, which remains the touchstone of Czechoslovak politics, sent a strong message of overall continuity to a society that has lived through years of economic and political stagnation, analysts here said.

The change in leadership here appeared to stir little public emotion. While the party newspaper Rude Pravo celebrated the event with a red banner headline over a half-page photo of Jakes, people here seemed to be more interested in preholiday shopping. Several residents who were asked said they knew little about Jakes but that they assumed he would continue Husak's policies.

Officials today portrayed the transition from Husak to Jakes as one of the smoothest in the history of East Bloc communism, planned months in advance, agreed upon unanimously by the leadership and designed by the veteran Husak to ensure perpetuation of his policies.

At a news conference following the party meeting, Central Committee foreign relations official Michal Stefanak said Husak, 74, had first suggested to the 11-member Presidium at the beginning of this year that he might give up his post as party chief at the end of the year while remaining as state president, a largely ceremonial post.

Stefanak said Husak believed that he was not physically capable of keeping both positions as he approached his 75th birthday next month and that one person was needed to devote all of his energy to directing the complex new restructuring program as party chief.

Husak's decision to step down was approved last month by the Presidium, Stefanak said. He insisted that Jakes, who had served since 1981 as a Presidium member and as Central Committee secretary specializing in the economy, was the only candidate and that Jakes had been approved unanimously by both the Presidium and the Central Committee.

Despite Jakes' pledge to pursue economic restructuring, the two-day Central Committee session did not take a decisive stance on a "complex document" outlining economic reform or on draft laws on the management of state enterprises, agriculture and cooperatives, officials indicated.

The plenary meeting had been expected to approve the measures, drawn up over the course of the past year and publicly debated this summer and fall. But Stefanak said the Central Commitee had returned the documents to the government for "further work" before the next session of the Federal Assembly, or parliament, next spring.

The action suggested that the party had been unable to reach full agreement on the measures, which encompass a partial decentralization of state economic management, a reform of prices and other steps designed to make the economy respond to market forces rather than central controls.

Party officials said today that during 1988, one-third of Czechoslovak industrial firms would conduct "experiments" in economic reform and that some steps toward political "democratization" also would be taken. But they did not spell out the planned measures.

Stefanak pointed out that the news conference was the first of its kind here to be organized after a Central Committee meeting. He said the practice would be continued -- a step, he said, that showed glasnost, Gorbachev's drive for public openness, had been adopted here.