UN human rights High Commissioner Ms Mary Robinson warned that next month's World Conference on Racism was condemned to failure unless delegations showed a sense of realism in setting the agenda.
With the United Nations-backed meeting under threat of boycott by the United States, Ms Robinson said countries must put their differences aside to ensure the meeting in South Africa was a turning-point in the fight against racism and xenophobia.
The UN High Commissioner for Human Rights, co-host of the August 31st -September 7th conference with the South African government, firmly restated her view that an attempt by Arab states to equate Zionism with racism would sink the Durban meeting.
At the start of a new drafting session in Geneva, she reminded conference planners that the UN had dealt with the issue a decade ago when it repealed a 1975 resolution equating Zionism, the ideology behind Israelis' belief in their right to a homeland, with racism.
"I believe that it is inappropriate to reopen this issue here and that anybody that seeks to do so is putting the Durban conference at risk," she said.
But she was more conciliatory on the other contentious issue looming over the conference - the question of slavery and whether past slave-trading states should pay reparations.
The US made it clear on Friday it would not go to Durban if either Zionism or the question of compensation for slavery were on the agenda at the conference.
The United States, whose views are echoed by most developed states, fears that any suggestion of financial compensation could expose it to a wave of litigation at home.
Some radical African-American groups have already raised the possibility of settlements along the lines of reparations paid out to victims - mainly Jews - of atrocities committed by Nazi Germany during World War Two.
Robinson said it was crucial the Durban conference fully address past wrongs, particularly slavery which flourished between Africa and the Americas for over 200 years until early last century.
"It is essential to recognise these wrongs...we must come to terms with the past to move forward," she said.
While avoiding going into detail, she expressed optimism some agreement could be reached between the mainly African states calling for compensation and former colonial powers.
"With good will and realistic approaches I feel the gap between the differing views can be bridged," she said.
But delegations, representing most UN states, have little time in which to whittle down two draft texts for a proposed declaration on racism and another outlining a plan of action.
Besides slavery and Zionism, there are several other controversial issues that could test the conference.
Arab states want to raise the question of Israeli occupation of Arab lands, while India is anxious to avoid the question of caste, a system of discrimination which has been officially abolished but which critics say is still rife in the world's largest democracy.