LONDON — Despite the failure of Foreign Secretary Geoffrey Howe's mission to South Africa and the threat of new demands for sanctions during the upcoming Commonwealth mini-summit, Britain is unlikely to agree to more than minor additional measures against Pretoria in the coming weeks, an aide to Prime Minister Margaret Thatcher said Wednesday.
"We're not going to budge on general sanctions," the aide said about Thatcher's reaction to the pressure expected as a result of Howe's failure to win concessions from the South African government. "We might end up with a gesture or two, but not much more."
The six Commonwealth leaders who are due to meet with Thatcher here Sunday to review possible action against South Africa are expected to push for sanctions. But like President Reagan, who has taken a stand against major trade sanctions, Thatcher also faces mounting domestic pressure.
The influential House of Commons Foreign Affairs Committee issued a report on South Africa on Wednesday, noting that Pretoria's continued refusal to accept negotiations to end apartheid would make it increasingly difficult for Thatcher to resist the sanctions option.
The main opposition Labor Party's national executive Wednesday passed a motion declaring Thatcher's South Africa policy an "ignominious failure" and charging that the policy has damaged the 49-nation Commonwealth and given comfort to proponents of apartheid.
Only One Opposed to Sanctions
Thatcher is known to be the only one of the seven heads of Commonwealth members attending the meeting who is strenuously opposed to comprehensive sanctions.
Zambia's President Kenneth D. Kaunda, who will attend the meeting, last week publicly lectured Howe about Britain's reluctance to impose sanctions and has threatened to withdraw from the Commonwealth if Thatcher fails to yield on the issue.
The other Commonwealth countries that will be represented at the three-day meeting are Australia, the Bahamas, Canada, India, and Zimbabwe.
The pressure for action from Kaunda and the other leaders is likely to increase after Tuesday's statements by South African President Pieter W. Botha, who angrily dismissed Howe's diplomatic efforts as "uncalled-for direct interference in our internal affairs."
Howe, traveling as an emissary of the 12 European Communities countries, called on Botha to release jailed black leader Nelson Mandela and legalize the now outlawed African National Congress in order to generate conditions for negotiations that could eventually lead to a dismantling of apartheid.
Howe returned empty handed to London early Wednesday from his second southern Africa trip this month and met with Thatcher later in the day. The government is expected to formalize its position for the Commonwealth mini-summit at a Cabinet meeting scheduled for today.
Review in September
However, Thatcher aides indicated that any substantive movement in Britain's policy on South Africa would more likely come during a review of the measures the European Communities will consider in September than at Sunday's Commonwealth meeting.
One member of her staff cited a ban on imports of South African uranium, coal, iron and steel, plus a ban on new investment as possible measures that Thatcher might be willing to agree to at that time.
Britain imports virtually no uranium from South Africa and does not permit new government investment as part of the limited sanctions it has already agreed to impose.
Thatcher aides also refused to characterize Howe's diplomatic mission as a complete failure, apparently clinging to the hope that Botha's abrasive news conference was somehow geared to domestic consumption in order to provide him latitude for future movement.
"The fact that he (Howe) has drawn a blank now doesn't mean there won't be something," a senior aide stated.
'The Man is Moving'
The aide noted the South African president faces a political party conference next month that carries important domestic impact and that dramatic action before that would seem unlikely.