What may be the first skirmish in a sticky fight over the Equal Rights Amendment in the Republican platform broke into the open today with Ronald Reagan and longtime conservative backers on the opposite side of the issue.

Reagan's chief of staff said the former California governor would accept a pro-ERA platform plank even though he personally opposes it, while conservatives began marshaling opposition to a platform draft that includes a lukewarm endorsement of the amendment.

The draft would put Republicans on record as reaffirming "our party's historical commitment to equal rights and equal opportunity for women, a commitment which made us the first national party to endorse the Equal Rights Amendment."

"We are proud of our pioneering role and do not renounce our stand," it adds.

Reagan, who once supported the ERA, has long opposed the amendment. But at a meeting called to announce the names of some additional Reagan domestic advisers and put pressure on President Carter to call off the Soviet grain embargo, Reagan chief of staff Edwin Meese said, "Obviously, the governor accepts what comes out of the platform committee even if that conflicts with his personal view."

The ERA, Meese said, is an issue on which "reasonable Republicans" could differ. He emphasized that Reagan would prefer a platform plank which opposed sexual discrimination without specifically mentioning the amendment.

The ERA may become the first in a series of controversial issues that puts Reagan, the darling of the nation's conservatives, at odds with longtime supporters as he tried to broaden his appeal to moderate Republicans, independents and Democrats.

It would be a battle that would create embarrasing uneasiness on both sides. North Carolina Sen. Jesse Helms, who offered a 22-plank conservative platform to the GOP's 1976 convention, has considered a similar effort next week when the platform committee meets in Detroit.

But his longtime associate Tim Ellis, a Raleigh, N.C. attorney, said in an interview, "At this point nothing has jelled. We don't want to get the reputation of being spoilers."

"Evidently, what Reagan's advisers are telling him is you have to spread your wings," said Ellis. "I'm of the mind you ought to do what's right on principle."

Ellis and other conservatives have been upset with the hiring of William Timmons, a key strategist for Gerald Ford four years ago, as Reagan's political director, and speculation that Reagan may pick a moderate such as Sen. Howard Baker as his running mate. They regard the GOP platform as the first stage in what one conservative called "the battle for the presidency" -- or the control of the reins of government should Reagan win next November.

The ERA is a highly symbolic issue for them. When Roy Brun, a Reagan delegate and member of the platform committee, found out about the draft ERA language, he sent a telegram to all other members of the committee. In the telegram, he threatened to introduce alternative language stating "the U.S. Constitution is too sacred a document to be changed" by adding the ERA after that amendment's original, seven-year extension period has passed.

"Personally, I would have hoped we could stay away from the ERA altogether in the platform," Brun said in an interview. Phyllis Schlarfly, a leader of the anti-ERA forces, echoed his feelings.

"I was shocked anyone would submit a draft plank with ERA in it," she said. "They must know we've got the votes to beat it."

The issue is one of the few that stirs widespread division in the party, which first endorsed the ERA in 1940. Earlier this week, 44 Republican members of Congress publicly appealed to Sen. John G. Tower, chairman of the party's platform committee, to keep a strong ERA-plank in the platform.

Tower last night would neither confirm nor deny the accuracy of the draft. ERA-plank language, which was supplied to The Washington Post by a member of the platform committee.

Recently, Reagan met with Sen. Nancy Kassebaum of Kansas in an effort to work out a compromise on the prospective ERA plank at the Republican National Convention.

Meese was vague about the specific results of this meeting but said he thought that Kassebaum and Reagan were in general agreement.

Reagan's statement on the grain embargo, released in Los Angeles and at a press conference held by Kansas Sen. Bob Dole in Washington, was another effort by Reagan and the Republicans to use the prestige of the likely GOP nominee to put pressure on Carter to change his policies before the election.

Last week, Reagan called for an immediate tax cut, and it sounded congressional Democrats. The Democrats quickly pledged to produce their own tax-cut bill by September.

On the embargo, Reagan said in his statement, "It has failed. Not only has it been ineffectual in dealing with the Russians, it also has severely hurt America's farmers."

Reagan called for immediate termination of the grain embargo, which he said had cost the American taxpayers $1 billion that could have been used to strengthen America's military defenses.

"If the president persists in imposing this unilateral, ineffective and financially painful burgen on the farmer. I will, when elected, fully assess our national security, foreign policy and agricultural trade needs to determine how best to terminate yet another of the inequitable and ineffective policies of the Carter administration," Reagan said.

In response, the Carter administration said the "embargo is a fundamental element of the economic sanctions imposed by the president on the Soviet Union earlier this year in response to the brutal Soviet invasion of Afghanistan," and said it saw "no reason for removing the embargo."

Reagan is vacationing in Mexico this week.

At what turned into a wide-ranging press conference, Meese commented on two other issues.

He said that the Reagan campaign would not be badly hurt if the courts decide to probhibit expenditures by independent committees aimed at electing Reagan. But Meese said it would be "grossly unfair" if the Federal Election Commission agreed to a Democratic Party request that would withhold federal election funds from Reagan's own campaign.

Meese said there was "no connection, no colusion and no encouragement" by the Reagan campaign of these independent committees.

Meese also termed "unfortunate" Reagan's refusal to address the national convention of the NAACP in Miami.

Meese blamed Reagan's failure to accept the invitation on a scheduling mishap.

"We're very sorry it happened," he said. "We hope to make amends later on."

The names of 100 men and six women who will serve as Reagan's domestic advisers were announced by Meese and Martin C. Anderson, Reagan's senior domestic policy adviser.

Anderson said that the work of the advisers will be closely coordinated with congressional policy committees that also are advising Reagan.