COLUMBIA, S.C. (AP) _ President Reagan, saying ''we haven't closed any doors,'' signaled Thursday that the United States has not ruled out imposing any sanctions against South Africa and still is considering limited steps.

White House spokesman Larry Speakes said there is a distinction between ''punitive, economic sanctions'' - which Reagan opposes - and ''other sanctions that are not punitive economic sanctions.''

The lesser steps might include denial of landing rights in the United States for South African planes, he said. ''I don't know, things like that,'' Speakes said.

Meanwhile, the State Department said late Thursday that Chester Crocker, assistant secretary for African affairs, would travel to London next week.

Bruce Ammerman, a department spokesman, declined to give specifics of the Crocker trip, including its date, but said it would be to ''consult with South Africa's principal trading and investment partners.'' CBS News said Crocker would discuss the possibility of coordinated sanctions against South Africa.

The comments by Reagan and Speakes suggested a shift in policy within the administration after harsh criticism from Democrats and Republicans alike about the president's South Africa policy speech Tuesday.

In that address, Reagan urged Congress and Western Europe to ''resist this emotional clamor for punitive sanctions'' and said ''we and our allies cannot dictate to the government of a sovereign nation, nor should we try.''

The speech was condemned by South African black Anglican Bishop Demond Tutu as ''quite nauseating.'' Sen. Richard Lugar, R-Ind., chairman of the Senate Foreign Relations Committee, criticized Reagan for a ''lack of leadership'' and said a tougher policy had to be adopted.

The House already has passed a package of sanctions, opposed by the White House, and Lugar's committee is considering them as well.

Reagan, posing for pictures at a haylift for South Carolina's starving livestock, was asked whether the United States might consider steps against South Africa in concert with allies.

''We haven't closed any doors,'' he replied, without elaboration.

Speakes, talking with reporters on Air Force One as it carried the president to a political speech here, noted that limited sanctions imposed against South Africa by Reagan last year will expire in September.

As those steps are reviewed, ''the decision would be made as to whether we want to add sanctions to that executive order,'' Speakes said.

''And whether we would seek to take any additional steps would be a product of a continuing review of the situation on the ground, any moves by the South African government toward change.''

He said Reagan's ''statement is clear that we oppose - that we think the South African government is wrong - in what they're doing.''

Since late 1984, more than 2,000 people, most of them black, have been killed in violence linked to apartheid, South Africa's system of legal segregation by which the country's 5 million whites dominate the nation's 24 million voteless blacks.

Speakes, distinguishing between broad, punitive economic sanctions and lesser steps, said, ''We've always said that sanctions would hurt the people that we're trying to help, and that would be our criteria.''

Earlier Thursday, Secretary of State George P. Shultz told a satellite news conference in Washington that if any sanctions ''are to be really effective, they must be done on a coordinated basis'' internationally.

Nations should ''see to it if any actions are needed they are taken in a coordinated way,'' Shultz said under questioning by reporters in Europe, South America and Canada. If U.S businesses are required to leave South Africa, he said, companies from countries not participating in sanctions could pick up assets at a ''fire sale - and laugh all the way to the bank.''

At the same time, Shultz reiterated the administration's strenuous objections to further sanctions.

Asked if restrictions imposed by allied nations would stir the administration to act with new measures of its own, he said, ''Obviously the views of our friends weigh heavily.''

But he added, ''We don't give anyone a blank check to write U.S. policy.''