Amid renewed efforts to prune Japan's huge government deficits, Prime Minister Yasuhiro Nakasone's Cabinet announced plans today to hold increases in the 1984 military budget to a maximum of 6.9 percent, a figure that is likely to mean further delays in the country's defense buildup programs.

The spending target, which sets an upper limit on defense appropriations next year of $12.3 billion, is important because it comes at a time when Japan is under pressure from the United States to shoulder a greater military burden more in keeping with its economic clout.

If previous years are any guide, analysts said, today's preliminary figure is almost certain to be whittled down substantially by the time the government makes its final budget decision in late December. Last year, for example, the initial estimate of a 7.3 percent increase for defense ultimately was rolled back to 6.5 percent in 1983 outlays of $11.5 billion.

Today's defense decision, still subject to internal government debate here, reflects a tricky political dilemma Nakasone faces in trying to honor his pledge to strengthen military ties with the United States while, at the same time, keeping a promise to Japanese voters to trim a massive cumulative bugetary deficit of $416 billion.

In setting spending ceilings for all government departments today, senior officials stressed that defense was given a clear priority over other appropriations, which, with a few key exceptions, are scheduled to be slashed by as much as 10 percent over 1983 levels. A more disproportionate boost for defense, they said, would risk reigniting criticism of Nakasone's hawkish stand on security issues, which, earlier this year, brought about a sharp decline in his support among the Japanese public.

The apparent lowering of Japan's defense sights, however, "will certainly bring dissatisfaction from the United States," said a prominent defense analyst. The more austere spending target, one of the lowest in two decades, will make it "virtually impossible" for Japan to meet weapons procurement plans outlined under its current five-year military buildup program, he said.

At stake are the purchases of more of the antisubmarine patrol planes, jet fighters, warships and other sophisticated military hardware that Pentagon officials say is necessary for Japan to meet its pledge to defend the country's airspace and sea lanes out to a distance of 1,000 miles by the end of the decade.

A perception that Japan is shirking its defense responsibilities has renewed calls on Capitol Hill in recent weeks for the Japanese to increase sharply their military spending. This comes at a time when Japan is piling up a record surplus on trade with the United States that is expected to hit $22 billion this year. American officials in Tokyo said they expect U.S. pressure on Japan to escalate in advance of an official visit to Japan by President Reagan, who is now scheduled to arrive here in early November.

The 1983-87 military plan calls for strengthening Japan's air and sea defenses with the purchase of 50 P3Cs beyond the currently ordered level of 25 aircraft. It also provides for the purchase of 75 F15s to add to 80 planes already ordered, plus an additional 14 destroyers and frigates, 6 submarines and 13 mine sweepers.

The 1983 budget, however, allowed for the purchase of only 13 F15s instead of 20 orginally planned, seven instead of 10 P3Cs, and two instead of three destroyers. To meet force levels envisioned on paper by 1987, analysts estimate that Japan would have to expand its yearly budgets by between 8 and 10 percent, something they regard as highly unlikely given Tokyo's fiscal austerity drive.