Republican governors today told Vice President Bush that they support the concept of a freeze on federal spending, with general agreement that the Defense Department and various entitlement programs should not automatically be exempt.

But Bush and some governors warned during a private meeting that a freeze on Pentagon spending might send the wrong "signal" as the United States and the Soviet Union begin talks on arms control early next year.

Bush was the featured speaker at the opening of the Republican Governors Association annual meeting where tax and budget-policy join politics as the main agenda items.

Warning of "tough and significant cuts," Bush told the governors, "The deficit must be brought down . . . . The president is as determined on this point as on anything I've ever seen him involved in."

He said Reagan "feels very strongly about these issues," and "if necessary, he will do what he has done so effectively in the past. He will appeal directly to the American people to seek their support. He was given a mandate in 1984 and is determined to control the federal budget and get this deficit under control."

Most of the action today came during a closed meeting between Bush, the governors and representatives of the Treasury Department and the Office of Management and Budget.

"The definition of a freeze can be in the eye of the beholder, but there was agreement on the general concept of a budget freeze," Pennsylvania Gov. Richard R. Thornburgh said. "An across-the-board and even-handed . . . budget freeze would be difficult with our diplomatic situation."

Thornburgh also said it would be difficult to freeze some entitlement programs.

"In the case of unemployment compensation, if the economy took a downturn, you couldn't have people in the benefits line and tell them all of a sudden that program had been cut out," he said.

Oregon Gov. Victor R. Atiyeh said the budget discussion centered around whether all programs should suffer equally or whether there should be variation within an overall freeze. He said there was "some political nicety to everybody being treated equally bad," including defense and entitlements.

Atiyeh said that the governors also had discussed with Bush the Treasury Department's tax simplification plan but that cutting the budget deficit is the first priority. He said the tax program is a lesser priority.

Thornburgh said the governors voiced no support for a tax increase to cut the deficit, calling it a solution "of last resort."

As for the tax-simplification plan, the governors said they told Bush that they don't like the idea of eliminating the tax-exempt status of industrial development bonds but that they are prepared to take their lumps along with everyone else.

"We'll share the burden, but we don't want to be singled out," said Iowa Gov. Terry R. Branstad.

In open session, Bush told the governors that the administration's focus next year will be on two things, "the economy and our relations with the Soviet Union."

He said Reagan "is . . . determined to work with the Soviet Union to achieve verifiable arms-reduction agreements."

Bush also said the administration believes that tax rates are too high and wants to lower them and simplify the system. "This will mean eliminating some of the complexities and some of the provisions of the tax code which have given one area of the economy a special break over other areas."