Frustration about the Iranian hostage situation has grown to the point that a strong majority of Americans -- almost 2 to 1 -- now supports military action, even if it imperils the lives of the hostages, according to a Washington Post national poll.

The hostage crisis, in addition, appears by far the dominant voting issue of the 1980 presidential campaign, with voters sending out conflicting signals regarding President Carter.

On the other hand, the poll suggests, many feel Carter has been too slow to act. Yet, relatively few voters seem to feel that either Edward M. Kennedy or Ronald Reagan, Carter's chief political opponents now, would do better than Carter at freeing the hostages.

The Post's poll was conducted from April 9-13, shortly after Carter broke relations with Iran, announced a trade embargo, blocked the entry of Iranians into the United States and expelled Iranian diplomats.

Those sanctions were approved by 6-to-1 among the 1,873 people interviewed by The Post. A great many felt the sanctions should have come much earlier in the 5 1/2-month crisis.

Asked whether Carter had used "too much restraint or the right amount of restraint in dealing with Iran," the public was evenly divided: 40 percent said too much, 40 percent the right amount and the rest voiced no opinion.

One-third of those interviewed believe the sanctions might help gain freedom of the hostages, but 42 percent think the steps would not make any difference. A sizable minority, 27 percent, felt the imposition of the sanctions jeopardized the lives of the hostages.

What this opinion poll cannot answer is the question of how the American public will feel if, indeed, there is military action in the coming months.Based on past episodes, the public usually rallies around a president who takes military action but sometimes becomes disenchanted afterward.

From the outset of the crisis in November, Carter has announced one specific aim -- the safe return of the hostages and avoidance of military action unless all other means fail. He continues to hold that position, and is seeking assistance from the allies in applying pressure on Iran in hopes that military action may be avoided.

In a January Washington Post poll, when the crisis was two months old, a majority of Americans rejected the use of force on the grounds that it could result in harm to the hostages. At that time, 51 percent said they favored taking no military action while 38 percent were in favor of setting a deadline and taking action if the hostages were not returned.

But now, those views have changed dramatically. The public's hope of getting the hostages back through peaceful means has largely disappeared.

The new Post poll asked which of these staements people agree with more -- "No matter how long the hostages are held in Iran, the United States should take no action that could threaten their lives" or "The United States should set a deadline for the return of the hostages, and take military action if they are not returned by then."

Thirty percent favored taking no action; 55 percent felt a deadline should be set and military action taken if the hostages are not returned by the deadline.

The Post poll and other recent polls show a rising national concern over Carter's failure to get results in dealing with Iran. Nevertheless, when asked whether Reagan or Kennedy would do better than Carter, the answer seems to be a sharp "No." Twenty percent of those polled said Kennedy would do better; 25 percent said Reagan would. In both instances, higher percentages felt the two candidates would not do as well as Carter.

One poll question posed this problem: "Suppose the Soviet Union were to interfere with our efforts to have the hostage returned. Which presidential candidate, Carter, Kennedy or Reagan, would you rather have dealing with that problem?" Forty three precent said they preferred Carter; 19 percent Kennedy and 27 percent Reagan.

The poll also asked whether Carter "has been truthful to the American people in discussing the situation in Iran" or whether "he has been misleading the people about events in Iran for political reasons." Sixty-three percent said he has been truthful; 27 percent said he has been misleading.

The public's views on how Carter is coping with the excruciating hostage problem seem to go a long way in explaining how the electorate is looking at the 1980 presidential election.

Other problems seem to melt next to the flame of feeling brought on by the hostage crisis. Inflation, for example, is clearly the number one personal concern expressed by the public. On that issue, Reagan is viewed as much more likely than Carter, by 48 to 32, to be able to restore the value of the dollar.

Yet, in the Post poll, Carter leads Reagan among registered voters by 51 to 42. Carter generally runs substantially ahead of Reagan among people who feel he can deal with Iran at least as well as his opponents. He trails by landslide proportions among those who feel he cannot.

In large degree the divisions transcend party lines. For example, Democrats who feel Reagan would be better than Carter in handling the Iranian crisis say they would vote for the Republican by 3 to 1, and Republicans who think Reagan cannot do as well as Carter getting the hostages back favor Carter by 7 to 3.

Nowhere is the forcefulness of Iran as a voting issue clearer than among independent voters. Among those interviewed who identified themselves as independents who are registered to vote, Reagan drew 90 percent support from those who feel he would be better able to deal with Iran. But he drew only 21 percent support from independents who felt he could not handle the problem as well as Carter, and 33 percent support from those who felt it made no difference whether Reagan or Carter were in charge.