Republican presidential candidate Pat Robertson reversed course yesterday and told the Federal Election Commission he would accept $4.5 million in federal matching funds after all -- at least for awhile.

A campaign statement added that because of Robertson's concern about the federal deficit, he might give the money back. It said the campaign would segregate the money while deciding whether to ask the FEC for an opinion about the possibility of returning the funds "to the American taxpayers" without incurring any liabilities.

Robertson had startled political experts Tuesday by sending a letter to the FEC saying that he wanted the government to defer delivery of the public funds for up to a month. Marion Edwyn Harrison, the campaign's FEC lawyer, wrote that the candidate had not yet decided whether to accept the public funding, and the spending limits and audit requirements that go with it.

Yesterday, however, another letter from Harrison arrived at the FEC withdrawing the request and a third letter directed that the $4.5 million Robertson has been certified to receive on Monday be wired to a Chesapeake, Va., bank.

R. Marc Nuttle, Robertson's campaign manager, said in the statement that the campaign is "extremely grateful" for the FEC's cooperation in studying the request. "However, because of the unprecedented nature of our inquiry, the FEC was unable to provide a full ruling on all points."

He said the matching funds law needs to be amended "to allow for more flexibility and freedom in how and when presidential candidates accept matching funds."

The statement added that "Robertson believes that the federal budget deficit is one of the most critical issues facing our nation today. His attempt to privately fund his presidential campaign has been an effort to reduce the current deficit."

The budget deficit was $148 billion for fiscal 1987 and is expected to be higher this year. The FEC estimates that about $175 million in public funds will go to presidential candidates this year. The money comes from taxpayers who designate $1 of their taxes for the special fund.

The campaign statement noted that Robertson intends to stay within the FEC spending limits for each state and said the campaign had spent less than half of the allowed amounts in Iowa and New Hampshire.

Robertson's campaign had raised $11 million by the end of September, the largest amount of any candidate except Vice President Bush. But it also had spent as much and was in debt at the time. Robertson aides said this week that total donations have climbed to $14 million.

The $4.5 million Robertson is due to receive is second only to the $5.7 million due Bush. A candidate is certified for matching funds by raising $5,000 -- in amounts of $250 or less -- in each of 20 states. The Treasury then will match each additional donation of up to $250 dollar-for-dollar.