WHEN THE SENATE majority leader, who is also a senior member of the Finance Committee, says Congress isn't likely to get around to tax reform this year, it is hard to be optimistic. That's true even if the speaker, Sen. Bob Dole, later attributes his early morning blues to the fact that he hadn't yet had his usual cup of coffee.

Sen. Dole is no enemy of tax reform. But as the prime architect of two recent reform bills, he does not underestimate the courage and energy needed to take on the many powerful economic and social interests that feel threatened by any change in this country's arcane tax code. And he could hardly feel heartened by the comments of his fellow Finance Committee members at the recent confirmation hearings of Treasury Secretary-designate James Baker. Each member in turn defended his favorite tax break from fringe benefits to macadamia nuts.

Only strong White House leadership could, as Sen. Dole observed, overcome these entrenched interests. That's especially true since many members, the senator included, feel that budget-cutting must take priority over reform. The Treasury's tax plan might well stimulate more revenues in the future, but it is designed initially to be revenue-neutral. That neutrality is a good check on special interests who would like to preserve certain tax breaks without raising other taxes to pay for them. But it also weakens support for the bill among members who feel that any real assault on the deficit will require more taxes.

Sen. Dole's insistence that budget-cutting come first wouldn't necessarily be damaging to the cause of tax reform if Congress could, as he still hopes, come up with a sensible, sizable budget plan within the next month or two. If the momentum behind a broad-based temporary freeze -- covering both defense and Social Security -- could be sustained, that might be possible. But already there are worrisome signs of slackening.

The White House won't get in front of any plan to curb either Social Security or defense. Many members won't buy more harsh cuts in social programs unless the Pentagon takes some real long- term losses -- not the usual flimflam in which inflated estimates are temporarily pared down. Sen. Dole freshened his concern on this point Friday, saying deficit reduction is in "real trouble" unless defense spending is held down.

Still, Pentagon officials are moving through congressional halls threatening to close this base or move that contract. Navy Secretary John F. Lehman Jr. demands that members of Congress, if they cut, decide "which do they want to give up, the Pacific or the Atlantic?" Defense Secretary Caspar Weinberger believes, says his spokesman, "that those who hope for 'success in bringing down the defense budget' really mean success in weakening the security of the country." Under this incredible onslaught, brave talk of restraining defense growth may fade.

It's too early to declare defeat on either the budget or tax front. But it may take a lot of strong coffee -- not only in the Senate but in the White House as well -- to get things moving.