The Senate will face an important test, possibly today, on a procedural motion to return the $180 billion defense procurement bill to the Armed Services Committee for further consideration. The issue is not, strictly speaking, defense, but whether the nation can strengthen its defenses in a way consistent with the equally pressing need to shrink the federal deficit.

While the size and composition of the budget for the next few years are still far from resolved, it is apparent to all sides that the administration's earlier path leads only in the direction of ever larger deficits. This leaves three choices--higher taxes, less domestic spending or less defense. While concessions must be made in all three areas, it is clear that defense cannot be totally exempt.

The procurement bill that the Senate is considering this week accepts all but a small fraction of the administration's record budget request. Since the White House has already conceded the need for further reductions, Sen. Carl Levin and other sponsors of recommittal argue that the bill should not go forward until the Budget Committee has set spending targets for defense and other areas. If the Budget Committee fails to act in a month, the defense bill would be returned to the floor.

Armed Services Committee Chairman John G. Tower argues, however, that no further cuts in weapons buying can be justified and that the slowness of the budget process should not be allowed to delay action on the defense bill.

The defense committees have in the past reported bills in advance of the budget resolution. The usually minor adjustments necessitated by budget ceilings were made later in the reconciliation process. But these are not normal times. Action on the defense budget will send a strong signal to the country about Congress' commitment to the discipline of the budget process.

If relatively substantial reductions in defense spending are later required by the budget ceilings, they should be made only after full consideration by Sen. Tower's Armed Services Committee. Hasty cuts made by amendment or in the appropriations process are not likely to reflect the care and expertise needed to make sure that available dollars buy the most effective possible defense.

The vote to recommit the defense procurement bill should not be regarded as a partisan issue or as a test of commitment to national security. It is an important first test of congressional readiness to make the hard--and careful--choices needed to assure that the country has both a strong defense and a healthy economy to support it.