Two key legislators yesterday displayed their impatience with the unwillingness of European NATO partners to pay more for defending the alliance.

House Budget Committee Chairman William H. Gray III (D-Pa.) complained that there is a "significant imbalance" between what the United States and its allies contribute.

Gray told Defense Secretary Frank C. Carlucci, making his first appearance before the committee, that the imbalance is particularly grating "at a time we're dealing with a fiscal crisis." He said the United States spends "more than 6 percent" of its gross national product on defense compared with 3.3 percent for NATO allies.

Carlucci, whose appearance coincided with President Reagan's participation in a NATO meeting in Brussels, replied that "I quite agree" the allies should do more, but said, "I don't think it is useful to berate the Europeans on this."

The defense secretary -- who in November had warned NATO allies in Brussels that there had to be a new division of labor -- chose to stress the positive yesterday, declaring that "90 percent of the ground forces come from European countries." He said some of the difference in burden-sharing occurs because the United States operates around the world, while while several European NATO partners kept their military forces at home.

Rep. Patricia Schroeder (D-Colo.), chairman of the House Armed Services Comittee's subcommittee on defense burden-sharing, said she agrees with Gray and urged Reagan in Brussels "to begin talking about changing the nature of our relationship with our developed allies. The reality is that we can no longer carry the burden of the free world's defense." She said that in fiscal 1988 the United States will spend $171 billion on defending NATO and Japan.

The Senate Budget Committee, in a separate hearing yesterday, turned to the Congressional Budget Office and two academics to address the concerns of a growing number of lawmakers that the burgeoning federal deficit requires NATO partners and Japan to spend more to defend their interests.

Robert F. Hale, an assistant director of the CBO, presented charts showing disparities in U.S. and allied defense spending.

In 1986, he said, the United States devoted 6.7 percent of its gross national product to defense compared with an average of 3.3 percent for NATO allies and one percent for Japan. Hale said U.S. defense spending in 1986 came to $1,155 for every citizen, compared with the average of $318 per person in the rest of the NATO alliance and $163 for Japan.

From 1955 through 1986, Hale continued, the United States spent between 5.1 and 10 percent of its gross national product on defense while NATO partners averaged no higher than 4.5 percent in that period. The most Japan spent on defense was 1.1 percent of its gross national product.

Paul Kennedy, a professor at Yale University and author of the best-selling book, "The Rise and Fall of Great Nations," termed the unprecedented U.S. federal budget deficits "alarming" and warned that in modern history the only great nations that increased their debt so markedly in peacetime was France in the 1780s, before the revolution, "and perhaps Germany and Japan in the 1930s before the decision for war. Those are not encouraging precedents," he said.

Former United Nations ambassador Jeane J. Kirkpatrick objected to letting economic conditions determine how much defense is enough, declaring that "positive trade with Japan does not protect against Soviet missiles."

PER CAPITA DEFENSE EXPENDITURES IN U.S. DOLLARS, 1986

Country.......... Expenditure .......% of U.S. Expenditure

United States......... $1,155 .......100%

Japan.................... 163 ........14

NATO Allies

Belgium................. $346 ........30%

Canada................... 308 ........27

Denmark.................. 322 ........28

France................... 511 ........44

Greece................... 232 ........20

Italy.................... 235 ........20

Luxembourg............... 145 ........13

Netherlands.............. 365 ........32

Norway................... 519 ........45

Portugal.................. 90 .........8

Spain.................... 113 ........10

Turkey.................... 53 .........5

United Kingdom........... 488 ........42

West Germany............. 453 ........39

NOTE: Defense expenditures for Spain and Japan use the national, not NATO definition, as reported in "The Military Balance, 1987-88."

SOURCE: Congressional Budget Office computations using data from "Financial and Economic Data Related to NATO Defense."