Unquestionably prodded by the successful, early May meeting in London of the North Atlantic Treaty Organization, the Moscow-dominated Warsaw Pact countries of Eastern Europe have already held one four-day session in Prague and scheduled another for June 1, site unknown.

The Prague session was privately billed by Communist operatives as a "business as usual" chat. However, Communist and Western experts are certain the major purpose was to review NATO's new goal for 3 per cent higher NATO spending annually to start the long process of building the alliance's conventional military power somewhat closer to that of the Warsaw Pact.

Under Moscow's whiplash, the Warsaw Pact states now have the highest conventional strength ever, particularly in forward-based arms and supply depots that may have made NATO vulnerable to "blitzkrieg" attack.

A key objective of the NATO commander, Gen. Alexander Haig, is to bring "front line" British and Dutch units forward to permanent positions far closer to the real Central European front, on the West German plain. That plan is designed to thwart a lightning Communist strike into Western Europe that would quickly outflank NATO forces assigned to "front line" duty, but in fact positioned far behind the front.

As usual, no announcement was made about the Prague meeting. But its military intent, according to experts, was to consider leapfrogging the new NATO decision by an immediate increase in its own strength.

The June 1 Communist session will bring foreigh ministers of the Warsaw Pact together, probably for another strategy preview of the Belgrade conference next month, a follow-up to the Helsinki agreement of 1975.

The failure of President Carter to compromise his bitter struggle with Congress over those 18 unwanted water projects reached a humiliating peak when not one of the 37 Democrats on the House Appropriations Committee spoke in his defense Wednesday, when the committee approved 17 of the projects.

Moreover, the White House made not the slightest effort to win economy-minded Republicans to the President's side. Neither Rep. Elford Cederberg of Michigan, ranking committee Republican, nor Rep. John Myers of Indiana, senior Republican on the public works subcommittee, has ever met any member of the overworked White House lobby staff. Neither was asked for help on the water projects.

More worrisome for Carter was the silence of his own Democrats despite his appeals for help (at least four separate appeals to Rep. Tom Bevill of Alabama, chairman of the public works subcommittee). Although a presidential veto of the bill is not certain (the Senate may cut three or four additional projects when it acts on the bill), Republicans are exuberant over the prospect.

"What we are soon going to be witnessing," Cederberg told us, "is Jimmy Carter running against his own Congress." That prospect also worries House Democratic leaders, headed by Speaker Thomas P. ("Tip") O'Neill and Majority Leader Jim Wright, who have repeatedly warned Carter they do not relish the idea of the overwhelmingly Democratic Congress's overriding the first veto of a new Democratic President.

While promising that no specific new proposals on strategic-arms reduction would be formally presented to the Russians at Geneva, president Carter nevertheless worried 10 select senators when he described to them what he felt was worrying the Kremlin.

The description came May 19 when senior senators of both parties were called to the White House to discuss the latest phase of strategic arms limitaton talks (SALT). Carter revealed nothing specific about Geneva but he did discuss the general international climate - including alleged Soviet concerns.

The President said the Russians are worried about U.S. "first-strike capability" - that is, U.S. ability to hit the Soviet Union with so much nuclear force it could not retaliate. In fact, the United States is not close to such capability, and the Russians know it.

Carter next suggested that the Kremlin is deeply worried about revived German militarism. That echoed a familiar Soviet propaganda theme even further removed from reality than U.S. first-strike capability.

"This was not the time or place to argue with the President," one defense minded senator told us. "But I, for one, was worried."

When Carter's remarks were followed by news accounts that the Russians fear the mysterious new first-strike capability, some senators began to suspect a plot hatched by Carter's disarmament advisers. Its purpose: to soften the way for major SALT concessions.

A footnote: At the May 19 meeting several senators told the President they saw no need for a quick arms-limitation agreement and urged him to stand fast. Although liberals were present, no dissenting view was expressed.