The new Soviet Communist Party leader, who held ''substantive'' talks with top Reagan administration envoys Monday, appears to be taking early command of the nation's foreign policy.
In a day that began with a hero's funeral for Mr. Brezhnev attended by dozens of foreign dignitaries, Party General Secretary Yuri Andropov met United States Vice-President George Bush and Secretary of State George Shultz for ''about 45 minutes to an hour,'' an American source said. It was the highest-level US-Soviet encounter since President Reagan took office nearly two years ago.
And early signs are that Mr. Andropov - a one-time diplomat and a specialist in Soviet relations with Eastern Europe - has moved much more quickly than did Leonid Brezhnev to claim the central role in foreign policy. Although Mr. Brezhnev took over as party leader in 1964, it was only in about 1970 that he emerged as the leadership's uncontested international affairs spokesman.
Besides Foreign Minister Andrei Gromyko, none of Mr. Andropov's Politburo colleagues was present at the meeting with the US envoys. An account from the Soviet news agency Tass portrayed the new party chief as the principal participant on the Kremlin side. As for Mr. Gromyko, he is by far the most experienced foreign policy hand on the ruling party Politburo but is viewed by most foreign analysts essentially as a technocrat. Also said by the Soviets to have been present was the late Mr. Brezhnev's foreign policy aide, Andrei Alexandrov-Agentov.
The precise division of foreign policy responsibilities among the post-Brezhnev leadership will take time to become clear. One hitch is that Mr. Brezhnev, once having secured center stage on international issues, assumed along with his party leadership the traditionally ceremonial post of Soviet president.
Mr. Andropov has become party leader. But the presidential slot has yet to be filled, and its post-Brezhnev significance has yet to be defined. In addition, the makeup of the Politburo itself is likely to change over the coming days or months as replacements are found for Mikhail Suslov (died in January), Brezhnev, Arvid Pelshe (reportedly died Nov. 12), and Andrei Kirilenko (reported to have resigned due to ill health).
In the US-Soviet talks here, there was no visible sign of a breakthrough on any of the substantive issues that increasingly chilled superpower relations during the final months of former Soviet leader Leonid Brezhnev. Instead, the very occurrence of the meeting Nov. 15, days after Mr. Brezhnev's passing, was seen as one indication the new Soviet leader wants cautiously to reciprocate the stated US hope for better relations in the period ahead.
There were also indications of a renewed Kremlin bid to warm the atmosphere of its relations with China. Earlier this year, Brezhnev, citing an unfriendly Reagan administration attitude as one catalyst, had embarked on a move to narrow the split with China.
The prominence of Soviet news media coverage of the condolence visit here by Chinese Foreign Minister Huang Hua suggests under Mr. Brezhnev's successor the Kremlin is, at least for now, decided on pursuing this course. East European sources say Mr. Huang, meanwhile, broke with the practice of other envoys when paying a formal condolence call on Soviet leaders. While even East European Communist chiefs spoke only briefly with Mr. Andropov, Mr. Huang is said to have tarried a full three minutes or so in conversation with the new party leader. The sources say Mr. Huang plans to stay on in Moscow until Nov. 17 and is scheduled to meet with his Soviet counterpart, Gromyko.
What sketchy information had emerged at time of writing on the Soviet-US meeting - with neither US nor Soviet officials willing to venture any immediate elaboration - suggested Mr. Andropov both wants to encourage whatever genuine softening toward Moscow the Americans may be contemplating, but is determined not to play the role of supplicant in any superpower thaw.
A statement from the American side said the meeting was ''frank, cordial, and substantive. It gave both sides an opportunity to exchange views on the state of their relations.''
Most foreign analysts here suspected the meeting's major immediate significance was that it had occurred at all. The Americans had been not at all certain the new party leader would oblige, particularly so soon after taking over, despite the omission in Vice-President Bush's arrival statement here of the kind of policy criticisms and harsh rhetoric that had come to characterize many Reagan administration statements about the Soviets.
The Soviet news agency account said Mr. Andropov had ''emphasized that the Soviet Union . . . is ready to build relations with the USA on the basis of full equality, noninterference, (and) mutual respect.''
In a development focusing attention on one substantive area of US-Soviet discord - the Afghan question - it was learned late Nov. 15 that Mr. Andropov had also received Pakistani President Zia ul-Haq.
Initial indications from Asian diplomats in touch with the Pakistanis were that the Afghanistan issue had been discussed in the meeting, which lasted about 40 minutes, but that Mr. Andropov had signalled no changes in Soviet policy.
In the view of some diplomats, however, the fact that the new party leader had chosen to meet with President Zia might signal a longer-term search for a palitable political resolution of the Afghan crisis. The diplomats said Soviet Foreign Minister Gromyko had also been present at the meeting, but that Mr. Andropov had done most of the talking for the Soviet side.