The United States ended 1984 with a $101.6 billion deficit in the broadest measure of its financial and trade relationships with the rest of the world, and may have become a net debtor nation during this quarter for the first time in 71 years, the government reported yesterday.

The $101.6 billion current account deficit -- which includes trade in merchandise and services as well as financial flows between Americans and residents of other countries -- is more than twice as high as the 1983 deficit of $41.6 billion, the Commerce Department reported.

Commerce Secretary Malcolm Baldrige said increasing payments of dividends and interest to foreigners who have invested in the United States means this year's current account deficit will be even larger.

This outflow of investment income, which has grown larger than income U.S. citizens receive on their overseas investments, is driving the United States toward its debtor status in the world. Economists predict that, by the end of the year, the U.S. debt will exceed that of Third World nations such as Mexico or Brazil, each of which owes close to $100 billion.

The United States was a net debtor last in 1914, when Americans owed $3.7 billion more to foreigners than foreigners owed to U.S. citizens.

Experts are unsure what this means, although one leading international economist, C. Fred Bergsten of the Institute for International Economics, said a massive American debt to other countries undermines its status as a political power.

Baldrige and Jerry Jasinowski, chief economist of the National Association of Manufacturers, agreed that the biggest cause of the current account deficit was the massive deficit in merchandise trade. This was listed on the current account report as $107.4 billion, less than a figure of $123.3 billion released earlier because the current account measure excludes some items.

"In contrast to the past, however, the merchandise deficit was not offset by either capital or services flows," Jasinowski said. "Instead of having it offset the trade account, they show some deterioration themselves."

The surplus in American sales of services -- insurance, banking, engineering, advertising and the like -- declined for the third year in a row. The decrease last year was $11 billion -- from $28 billion in 1983 to $17 billion.

"The surplus in services hit a peak of $41 billion in 1981, the last year it was large enough to offset the trade deficit," Baldrige said.

That year the United States recorded a $6.3 billion current account surplus.

American banks' overseas loans increased by $7.3 billion last year compared with $25.4 billion in 1983. The decline was caused by a lessening demand by industrialized countries for loans and a reluctance on the part of U.S. banks to increase their loans to debtor Third World nations.

But foreign investments in the United States, especially of U.S. Treasury securities, increased markedly. Inflows of foreign capital nearly doubled, to $21.2 billion from $11.3 billion in 1983. Purchases of Treasury bills by foreign investors hit a record $22.5 billion, almost three times the 1983 figure of $8.7 billion. The Commerce Department said these investments were encouraged by high interest rates and the removal of the U.S. withholding tax on interest paid to foreigners.

Aside from foreign investment in Treasury notes, foreign deposits in U.S. banks were high in the first half of 1984, but dropped in the last six months of the year. Nonetheless, they increased $27.6 billion last year, although that is less than the $49.1 billion increase reported for 1983.