House and Senate Republicans are loading their entire legislative agenda into a single, omnibus budget bill - a bill they acknowledge President Clinton is certain to veto at least the first time around.

That strategy means Congress and the White House are headed for a series of showdowns this fall, and at least part of the government could be shut down for a while if neither side blinks.At stake is the near-term fate of several Republican proposals, including restructuring of the Commerce Department and the State Department, a phaseout of federal farm subsidies and elimination of the Federal Maritime Commission.

What is intended as a technical budget blueprint also has, or is expected to have, sections on international shipbuilding, ocean shipping deregulation, cargo preference, local rail-freight grants, Alaska oil exports, aviation fuel-tax exemption, allowing government contractors to permanently replace striking workers and changes in tax and trade laws.

GOP leaders say they won't give in and Mr. Clinton will be forced to eventually accept many of their policy changes. The Senate's second-ranking Republican said that if the president vetoes their individual spending bills and then vetoes the budget reconciliation bill, Republicans will put many of the same disputed policy provisions in a yearlong, stop-gap spending bill. Called a continuing resolution, the stop-gap bill is designed to keep the government operating at a reduced level. He said the president will have to accept one of the approaches.

"This is what the Democrats and President Clinton are not thinking about," Sen. Trent Lott, R-Miss., said Friday. "They think we're going to send the president a clean continuing resolution, just at the lowest (spending) level."

But Sen. Lott said the Democrats "haven't seen anything yet. This bill could have all sorts of things on it that they are going to hate. We're not going to make it easier for them."

In addition to the policy changes, the budget reconciliation bill will contain tax changes and other legislative bits and pieces necessary to make final spending numbers match revenue and borrowing limits.

Tied into it will be the issue of raising the national debt ceiling, to $5.5 trillion from $4.9 trillion. It would put the president in the difficult position of having to sign the bill or risk a shutdown of the federal government, while a compromise - if there is to be one - is negotiated. Failure to raise the debt ceiling could have the effect of handcuffing Treasury Department securities sales, a prospect some fear would disrupt international money markets.

If a compromise is reached, Republicans are vowing it won't be without some major policy changes they want. In particular, House Republicans are digging in their heels on a bill breaking up the Commerce Department into smaller agencies.

"We are all aware of the magnitude of change coming together here at the end of this Congress. It is amusing to me that something so big as the elimination of the Commerce Department gets overwhelmed by the change that is going on," said House Majority Leader Rep. Dick Armey, R-Texas.

"You will see a Cabinet chair taken out of the Cabinet room and put in a museum somewhere," he said.

If Mr. Clinton vetoes the reconciliation bill, or if the Senate is unable to accept inclusion of Commerce dismantlement in the budget measure, House Republicans say they will insist on including the bill in any continuing resolution. The president will have a choice, they say: Either he shuts down the government or Commerce is consolidated. Mr. Lott said breaking up the Commerce Department is also a priority for Senate Republicans.

House and Senate Republican leaders met Friday morning to discuss strategy for the remainder of the year. Mr. Lott said they decided to hold all individual appropriations bills that the president has threatened to veto and send them to the White House at the last minute, along with the budget reconciliation bill and a continuing resolution.

"This morning we came up with a list of 45 policy items that are on these bills," Mr. Lott said. "Some of them I would like to see stay on the measures. Some, I'm sure, I would want to get rid of."

One item he doesn't like that is expected to come up in debate is a provision ratifying an international shipbuilding treaty negotiated last year.

The Republican plan on the Commerce Department would take the department's export promotion functions and consolidate them with trade-related programs

from other agencies. They would be under a new agency headed by what is now the White House's Office of the Trade Representative. The National Weather Service and science-related functions of Commerce would be transferred to a new science agency.

A total of 38 programs and smaller agencies and 6,000 jobs would be eliminated. Republicans estimate the moves will achieve $8 billion in savings over seven years.