Israeli Defense Minister Ezer Weizman pressed his country's case for an additional $12.5 billion in U. S. arms at the Pentagon yesterday but won no commitment from Defense Secretary Harold Brown.

Instead, defense official said, Brown confined himself to hearing Weizman out on subjects ranging from hoped-for Arab-Israeli peace talks to the specific aircraft and tanks requested under Israel's 10-year defense plan.

That plan, sources, said, would take Israel through 1985 and cost about $12.5 billion in additional U. S. arms if the wish-list were fulfilled. With eight years to go on that 10-year plan, the annual cost between now and 1985 would run about $1.5 billion, Pentagon sources said. This would mark a 50 percent increase over the current U. S. arms flow to Israel.

Carter administration officials believe the plan overstates Israel's military needs. Brown told a House Budget subcommittee last week that "Israel remains able through 1982 or 1963, which is as far ahead as you can projects, to defeat any combination of the Arab countries."

The context for Brown's assessment was what would happen if the administration's proposed aircraft package for the Mideast were approved by Congress. That package calls for selling 75 F16 and 15 F15 fighters to Israel; 50 F5E fighters to Egypt, and 60 F15s to Saudi Arabia.

Weizman started his day at the Pentagon by receiving a 19-gun salute and honor-guard review as snow drifted down on the River Entrance parade ground. From there, he and his aides met with Brown, lunching in the defense secretary's dining room.

Early in the sessions, which extended to a dinner in Brown's dining room, Brown stressed the administration's interest "in a high degree of military security for Israel," according to Thomas B. Ross, Pentagon spokesman.

But from Brown's standpoint, defense officials said, the sessions with Weizman were "largely listening. There were no decisions, no commitments made."

Although Pentagon officials have not disclosed the items on Israel's shopping list, sources said they include additional aircraft, including KC135 tankers for aerial refueling; money for producing tanks in Israel; thousands of U. S. tanks and armored personnel carriers; and a vast array of other modern weapons.

If Israel got all the weapons it is seeking, specialists have said, the country could wage a "war of anniliation" against Arab nations and reach far beyond the borders of past wars with long-range aircraft. Also, Israel is requesting so much ammunition that specialists believe it could win a war without coming to the United States for resupply, as was the case during the Yom Kippur War of 1973.

In addition to talking at length with Secretary Brown, Weizman called on top officers of the Army, Navy and Air Force at the Pentagon to discuss military matters.

Carter administration officials had said that they consider the proposed aircraft sales to Israel, Egypt and Saudi Arabia as a package that cannot be unwrpped for fear of disturbing the arms balance they strived for in recommending the deal to Congress. Therefore, Weizman's pleas yesterday and subsequent ones are not expected to bring any immediate change in the administration's proposed arms sales to Israel.