PRAGUE -- Milos Jakes, Czechoslovakia's newly installed communist leader, may lead a cautious move toward the political and economic changes advocated by Soviet chief Mikhail Gorbachev, but is more likely to defend the orthodox party establishment that has ruled since the 1968 Soviet-backed invasion, diplomats and political activists here say.

Jakes, who replaced Gustav Husak as secretary general of the Communist Party last week, has built his career as an efficient but colorless party bureaucrat who loyally served reform leader Alexander Dubcek as well as his successor, Husak. Jakes' connections to Moscow and Gorbachev appear strong but his cautious, dry temperament is virtually the antithesis of the Soviet leader's style.

The ambuiguity of the record and the seeming logic of a closer alignment between Prague and Moscow have led many Czechoslovak dissidents to a cautious optimism that Jakes will begin to crack the political and economic freeze imposed on the country by Husak for 18 years. Jakes pledged in his first speeches to press ahead with a moderate program of economic reform as well as "deep democratization."

At the same time, some western diplomats and Czechoslovak observers here caution that Jakes' rise to power may represent a closing of ranks by the orthodox establishment in the party, intended to ensure its control over the transition from an aged Husak toward policies more akin to Gorbachev's.

In that case, Jakes, 65, may merely manage a retrenchment of the old leadership, braking any meaningful reform measures, and continuing Czechoslovakia's relative resistance to the change in the socialist system sought by Gorbachev. "This could mean that the orthodox line has ensured its continuity beyond the inevitable passing of an aging Husak," a veteran diplomat said. "Jakes could delay a real transition of leadership here for many more years."

Suggestions that Jakes will pursue a conservative line appear partially supported by a recent slowdown in the move toward economic reform launched by Husak during his last year in power. According to a schedule drawn up by the party, a "complex document" spelling out the specific policy measures and providing a timetable for their enactment was to have been published this fall and approved by a meeting of the Central Committee last week.

That meeting, however, failed to act on the long-awaited document. It also returned to the government "for further work" draft laws to reorganize the management of state enterprises, agriculture and cooperatives. A resolution adopted at the meeting, which did specify various reform measures and dates to carry them out, seemed to be a substitute for a program not yet agreed on, diplomats and Czechoslovak journalists said.

"The reform has clearly slowed down," said a diplomat. "We seem to have entered another period where they've decided they don't have to go much further."

It is unclear to what extent Jakes, as Central Committee secretary in charge of economic affairs, may be responsible for the sluggish movement. But one account circulating in Prague suggests the party leader has been engaged in a struggle with Prime Minister Lubomir Strougal to control the reform. Strougal is widely viewed as the reform's chief architect and the strongest proponent of Soviet-style change within the ruling party Presidium.

According to this account, regarded as plausible by senior western diplomats, Jakes won a confrontation with Strougal, strengthening the party's control over the program of change -- excluding non-party technocrats and academicians who had previously worked on it.

There are widespread expectations that Strougal may be forced to resign.

In his first speeches as party leader, Jakes offered strong assurances that the reform would go forward. "A categoric imperative of the immediate future is to elaborate the program of transition to the new economic mechanism and to start its implementation without delay," he said. He added at another point that "there can be discussions and polemics only about how to prepare and carry out the revolutionary changes," not whether they should be done.

However, he also stressed the need for "consolidation of order and discipline" in the economy and society as "an important prerequisite" for any change.

"Jakes is a man with a strong preference for order and for seeing things orderly done," said Jiri Hajek, who was foreign minister under Dubcek and who met Jakes in the 1950s. "He will be very cautious, and he will insist on strict party control of any reform."

Born into a peasant family, Jakes -- pronounced YA-kesh -- was trained as a mechanic and designer in the 1940s at the famous Bata textile enterprise in the town now called Gottwaldov. He came to Prague in the early 1950s with his wife Kueta and two sons as an official in the Communist Youth organization, then spent several years studying at the Soviet party college in Moscow.

Jakes cut his sharpest profile from 1968 to 1977, when he was chairman of the party Central Control and Auditing Commission, the chief internal disciplinary body.

Named to the post by Dubcek at the beginning of his liberalization drive, Jakes first carried out the rehabilitation of a number of liberal party activists. Yet, he later supervised the wholesale purge of about 500,000 party members following the Soviet-led invasion and the ouster of Dubcek.

By most accounts, Jakes was more zealous as a represser than as a reformer. Hajek remembers Jakes as aligning himself with conservative forces in the party during the Dubcek era even before the Soviet-led invasion, and as having sought in the early days after the invasion to set up a neo-Stalinist "workers-and-peasants government" even more aligned with Moscow than the one that eventually emerged under Husak.

In 1973, there were reports in West European media that Jakes had been so aggressive in liquidating party cadres that Husak forced him to take an extended leave. Husak justified the decision to the Presidium by saying that Jakes had suffered from a tubercular lung ailment and needed treatment in a sanatorium, according to an account at the time in the Italian newspaper Corriere della Serra.

Ladislaw Lis, who had hired Jakes for his first post in Prague, was rehabilitated by his former lieutenant in May 1968, then expelled under his supervision a year later.

Lis, the former chief of the party youth organization, said he had regarded Jakes as a friend and loyal supporter. But when party elders fired Lis, Jakes deserted him and even signed a petition to have him evicted from the housing block where they had lived and socialized.

"Jakes is a very ambitious man who calculates very carefully profits and risks before taking any step," Lis said. "He has always followed shifts in the political winds swiftly and without any hesitation. That is why he has survived and risen."

Remarkably, both Lis and Hajek are guardedly optimistic that Jakes will pursue moderate reforms. Their assessments are based to a large extent on what they say is the new leader's strong loyalty -- and apparent close connections -- to the Soviet Union.

As the Central Committee's secretary for agriculture in the late 1970s, Jakes probably was in touch with Gorbachev, who held the same position in the Soviet Union. Jakes also met top Soviet leaders during a high-profile trip to Moscow in November 1986.

At the same time, Jakes reportedly has long been a key patron of a highly successful model cooperative farm, Slusovice, whose innovative, flexible management -- in marked contrast to the rest of Czechoslovak agriculture -- has drawn the attention and praise of one of Gorbachev's leading economic advisers, Abel Aganbegyan.

Diplomats doubt that Jakes has a strong personal tie to Gorbachev, who held an unusual personal meeting with Strougal during a visit by the prime minister to Moscow in mid-November. At the same time, many observers say Jakes' course may depend to a large degree on that of Gorbachev.

"If Gorbachev survives and goes ahead with reform, Jakes in the end will do the same," said Lis. "He will do so because he is ambitious, and he will see that his best interest lies in following a strong leader in Moscow."