It is D-Day today for South African rugby supremo Louis Luyt as the deadline of ultimatum issued by Mluleki George, of the National Sports Council (NSC) expires.

George's NSC has given the national executive committee of the South African Rugby Football Union (SARFU) until today to resign, failing which it has pledged to launch a campaign to isolate South African rugby and scupper pending tours by international rugby teams, including one from Ireland due to start later this month.

In what observers see as a tactical manoeuvre George has let it be known that the NSC might settle for the resignation of Luyt alone, thereby creating pressure within SARFU for Luyt to quit in the interests of South Africa rugby. "If Louis Luyt resigns we might be able to talk business," George has said. "If he doesn't go, it will be a sad day for our country."

Already one of the most powerful of the affiliated unions in the SARFU, Natal, has called on Luyt to resign for the sake of rugby, thereby strengthening George's hand in SARFU. Apart from being NSC president and an ANC parliamentarian, George is the president of the Border Rugby Union, another SARFU affiliate.

The contest between Luyt - who is president of SARFU - and George has all the markings of a clash between the proverbial immovable objective (the physically big and intellectually robust Luyt) and irresistible force (George, who represents the African National Congress in Parliament and who therefore has the ear of powerful forces in the ruling party).

But the struggle between the two may be more complex than that in reality. Luyt is a shrewd tactician as well as a determined fighter: he bought time last month by agreeing to meet the NSC executive after it first issued its ultimatum on March 28th and surprised observers by attending the meeting after indicating that he would stay away.

He may make another move to gain time or defuse the situation. George has yet to demonstrate that he can he can mount a effective campaign of mass protest against the present SARFU administration, including blockading international airports to prevent the arrival of visiting rugby teams - a threat made by George's ANC colleague in Parliament, Lulu Xingwana - as part of a concerted strategy to persuade rugby bosses abroad not to send teams to South Africa.

Luyt has already dismissed George's threats, saying during an interview with New Zealand television in April that the NSC is not as powerful as people think and that it is about time that it is taken on. The NSC is not a statutory body and has no statutory powers. Its legal leverage against Luyt, who decisively defeated George in a contested election for SARFU's presidency last November, is thus minimal.

A court decision last month granting SARFU's application for a judicial commission of inquiry into SARFU has further strengthened Luyt's hand, legally speaking. But since then two events have strengthened George's hand politically: first, a declaration by the powerful Congress of South African Congress of Trade Unions that it would support an NSC-led campaign to break Luyt's hold on South African rugby if he does not resign voluntary; and, second, a similar declaration of solidarity from Sports Minister Steve Tshwete.

But the immediate arena of the struggle will be a full meeting of all SARFU affiliates today. The question that all rugby enthusiasts are asking is whether the anti-Luyt forces can muster enough strengthen to persuade or force him to resign. Observers point out that at the last full meeting Luyt decisively defeated his challengers for the presidency, securing 33 votes against seven each for George and Keith Parkinson of the Natal Rugby Union.

But the situation has changed since then and the balance of power may have shifted against Luyt. Against that, however, several of the smaller (and more conservative) unions are in thrall to SARFU financially and they may check any move to oust Luyt, who is the president of South Africa's richest rugby union, the Gauteng Golden Lions, is SARFU's paymaster.

Fears in New Zealand and Australia that the dispute will jeopardise the Tri-Nation series - which they contest with South Africa - has increased pressure on all the protagonists and on Luyt in particular. New Zealand Rugby Football Union chief executive David Moffett has said: "South Africa has obligations to not only us through the joint venture agreement that we have with them but also obligations to (Rupert Murdoch's) News Ltd . . . We find it difficult (to believe that Louis) Luyt who helped put that all together would put it in jeopardy."

Luyt, who negotiated with the ANC to end the rugby boycott in the 1980s, now finds himself fighting to prevent that boycott from being reimposed. His response today will clearly be crucial. Another critical unanswered question is what stance the ANC-controlled government will take in event of protest action from NSC. Much will depend on whether it chooses to act as ringmaster or gladiator.