NEVER HAS a nation had such a clear warning of danger -- and ignored it so completely and stupidly. For almost two years, the Carter administration has been told publicly (by concerned members of Congress, among others) that one of the best defenses against a cutoff of oil imports would be to fill the strategic petroleum reserve (SPR) authorized after the 1973 embargo.

Now, as Iraq and Iran engage in a shooting war and oil shipments through the strategic Strait of Hormuz are threatened, the caves in Louisiana and Texas designated for the SPR are mostly empty, holding a mere 92 million barrels.

Even that much is significant in this crisis: If imports should drop by half -- say to 3 million barrels a day -- oil could be drawn out of the SPR to ease the pain. Thus, if the SPR had to be tapped for one million barrels a day, it would last for about three months.

The shame -- even the crime -- is that the SPR is not 10 to 20 times that size by now. Time after time, a bipartisan group that included Sens. Bennett Johnston (D-La.), Bill Bradley (D-N.J.), Robert Dole (R-Kan.) and Henry M. Jackson (D-Wash.) warned that the administration was jeopardizing U.S. security by bowing abjectly to Saudi resistance to filling the SPR. Strategic stockpiling was suspended in November 1978 in the wake of the Iranian revolution.

Bradley put it this way last June: "The risks of carrying an inadequate reserve are simply not acceptable. We must build that stockpile, given the likelihood of a major supply interruption during the next decade and the magnitude of the expected economic losses to the United States."

IT WASN'T AS IF the Carter administration didn't know the score. On Dec. 12, 1979, in secret testimony (later declassified) before a Senate energy subcommittee, Julius L. Katz, then an assistant secretary of State, said: "I wish we had filled (the SPR) three years ago . . . Again we are always going to be in this situation of wishing we had done something else."

And Undersecretary of Energy John M. Deutch added: "There is no question about it; we will be very sorry that we have not filled SPR."

At about the same time, a senior Carter administration eneragy official who favored boosting the supplies in the SPR said to me (when I promised not to identify him): "The president does not want to build the SPR because he fears it will jeopardize the Saudi production level. I believe the Saudis will interpret that as weakness, and we should go ahead on the SPR. We've got to start sometime."

But nothing did start until last summer, when token stockpiling at the rate of 100,000 barrels a day was mandated by congressional legislation requiring Carter to take that much out of naval oil production from Elk Hills. This was the price that Carter had to pay for his synthetic fuels legislation.

Now, nothing could be clearer than the need to boost that 100,000-barrel-a-day figure to a minimum of 300,000 barrels a day. Sen. Johnston says that the SPR caves can take in at least 500,000 barrels a day -- and that, even with the lessening of the oil glut as a result of the Iranian-Iraqi situation, there would be no trouble in acquiring 300,000 barrels a day.

But will the administration change its gutless attitude, even now, and build the SPR into something meaningful?

A discouraging hint is the testimony by Deputy Energy Secretary John Sawhill last Monday that the United States has a surplus of oil large enough to withstand an interruption of 164 days, a period longer than during the 1973 embargo.

THIS TRICKY formulation could induce a false sense of security. Sawhill had reference to private stockpiles owned by the oil companies which are at record levels. It's certainly fortunate that private stocks are that high. But short of war or national emergency legislation, that's not the same as having a government-owned emergency reserve.

"What Sawhill did on Monday was to hold up a fig leaf, nothing more," said a staff man on Capitol Hill.

What can be done now to retrieve the situation? Johnston and others on Capitol Hill have personally appealed to Carter through Energy Secretary Duncan and Sawhill to direct SPR officials to make commitments for oil over the present 100,000-barrel-a-day limit. Carter has that authority.

We are in a real crisis: Even without overt military action, the Strait of Hormuz is effectively blockaded because insurance companies have declared it a war-risk zone. With high premiums thus necessary for any tankers to go through, the traffic through the gulf will slow to a trickle, at best.

Careful observers will note that the present supply-line crisis did not take place because of Arab-Israeli tensions, usually cited as the basic reason for tip-toeing around the Saudis.

How long will it take before President Carter sets aside his misplaced fears of Saudi reaction, and moves to protect the interests of this country by giving a complete go-ahead to filling the strategic petroleum reserve?