IN a move that could shift the balance of political forces in South Africa, the liberal Democratic Party is considering attending a unity conference of anti-apartheid forces next month."We have always been in favor of a national convention to resolve the country's problems," Democratic Party leader Zach de Beer said in an interview. "If we are invited, we are prepared to look at the proposals, and we might decide to go." Caught between the liberalization of the ruling National Party and the socialist-leaning African National Congress (ANC), the Democratic Party has kept a low profile since President Frederik de Klerk began fundamental political reform 18 months ago. "If the Democrats come in now it will counter the more radical demands in the anti-apartheid movement and increase pressure on De Klerk to make concessions," says a Western diplomat. The ANC, which will be the largest group at the conference, is going out of its way to encourage the Democrats to attend. "They would be most welcome," says Pallo Jordan, ANC director of information, adding that the only precondition for attending the conference is a proven anti-apartheid record. In recent weeks, the ANC has blurred its preconditions for attending next month's conference and broadened the range of participants to include business, church, and even sporting organizations. Referred to as the "Patriotic Front" conference, it is seen by anti-apartheid leaders as a necessary step in unifying the disparate forces opposed to the ruling National Party before an all-party conference is held later in the year. The term Patriotic Front refers to an election alliance entered into by the two liberation movements in neighboring Zimbabwe before independent elections in 1980. It is seen as the forum for rallying support for an elected constituent assembly as the best mechanism for drawi ng up a new constitution. The conference is being jointly convened by a committee consisting of representatives of the ANC, the rival Pan Africanist Congress (PAC), and the black-consciousness-oriented Azanian People's Organization (AZAPO), and their respective trade union wings. The three groups took part in a similar conference in December 1989 - known as the Conference for a Democratic Future - which laid the groundwork for a closer relationship but failed to achieve a breakthrough. Democratic Party members were observers at that conference. PAC spokesman Barney Desai told the Johannesburg-based daily Business Day recently that all those hoping to participate must be in favor of an elected constituent assembly as the mechanism for drawing up a new constitution. The PAC has shunned contact with the government, but says it is prepared to negotiate the specifics of a constituent assembly. The government favors the all-party conference, a nonelected body, as the forum for drawing up the constitution. The all-party conference will discuss the form of transitional arrangements, a set of constitutional principles, and the forum that will draw up the new constitution. The Democrats support the government position but are developing an alternate position that would endorse the idea of an elected constitutional conference, subject to veto by the majority party at the conference (probably the ANC), and the majority ruling National Party in Parliament. The Inkatha Freedom Party of Chief Mangosuthu Buthelezi has already said it will not attend any conference whose objective is to advocate an interim government and constituent assembly. Inkatha rejects both concepts, favoring National Party proposals for negotiating a new constitution. Some Democratic Party legislators say that the political fallout of the Inkathagate funding scandal has increased the possibility of the party taking part in a broader anti-apartheid initiative. "Up to now, most of our energies have gone into keeping the party together rather than making key strategic and tactical decisions," says a Democratic Party legislator. "Now, our chance has come. We must go to the conference." The Democrats support the idea of a transitional administration providing that all changes are constitutional and that continuity is ensured by the continuation of the present white minority-controlled Parliament. They say the party could make a major contribution to the "Patriotic Front" through its expertise, and experience, and its track record of adherence to the rule of law and democratic values. It would represent a shift within the Democratic Party toward those advocating a closer relationship with the ANC and a defeat for those who propose a closer parliamentary alliance with the National Party. A bid by about a dozen of the Democratic Party's 32 elected legislators to commit the party to such an alliance was defeated earlier this year. The Democrats' dilemma was captured by the recent publication of the National Party's constitutional proposals, which are almost identical to the Democratic Party policy. Mr. De Beer, the Democrat Party leader, says the National Party had now adopted almost all the Democratic Party's policies. But he says this does not mean the Democrats will join the National Party. He says the recent funding scandal has demonstrated the desirability of the Democrats retaining a "watchdog" role. Democratic Party attendance would represent a fundamental change in the nature of the proposed conference which has been perceived in the past as an attempt to consolidate black opposition to the De Klerk government and foster a broader black unity. "Previously, the Patriotic Front initiative appeared to be an attempt to perpetuate mass action politics and precipitate a two-party showdown," says Mervyn Frost of Natal University's political science department. "But the participation of the Democrats puts the whole thing in a new light. As an independent player they will raise the tone of the proceedings and ensure than all the thorny issues are tackled," Professor Frost says. The conference was originally to have been held in March this year but has been postponed several times due to divisions between the major participants and problems with funding. It is now scheduled for early October. The Democratic Party, which holds 32 of the 166 elected seats in the white house of Parliament, won about 450,000 of the 2.2-million votes cast in the last national ballot in 1989.