CARACAS - (AP) -- Opposition leaders urged former President Jimmy Carter on Sunday to extend his peace mission here so he can witness a march
  against President Hugo Chávez in hopes of preventing violence.

  Thousands of anti-government protesters are expected to march Thursday on Miraflores, the presidential palace. Chávez supporters often entrench
  themselves outside the palace to repel protesters.

  A SALVAGE MISSION

  Carter, who arrived Saturday at Chávez's invitation and planned to leave the day before the march, is seeking to salvage reconciliation talks between the
  leftist government and its opposition. The government-sponsored dialogue began after an April coup that briefly ousted Chávez.

  Carter met Sunday with Vice President José Vicente Rangel, media owners, labor bosses and Roman Catholic Church leaders.

  He was to meet with Chávez later Sunday, state news agency Venpres reported.

  Should Carter stay for the march, ''violent pro-government groups won't dare attack men and women on the streets demanding justice, peace and
  democracy,'' eleven opposition parties said in an open letter to Carter, which was published Sunday in El Universal.

  Labor and media leaders who met with Carter said the American offered to have members of his team stay for the march.

  Carter was declining comment until his visit ended.

  U.S. Ambassador Charles Shapiro urged Venezuelans to accept help either from Carter or from the Organization of American States.

  ''Without an effective and sincere dialogue, polarization will continue,'' Shapiro said in a Sunday interview with El Universal. ``There will always be
  differences, but having a divided country is dangerous for Venezuela, which is on the brink of a social explosion.''

  Prominent opposition politicians and business leaders have abandoned or refused to join the dialogue, arguing that Chávez isn't serious about
  compromising.

  Many were skeptical that Carter's visit would help.

  ''I'm not optimistic. I think Mr. Carter is wasting his time in Venezuela,'' said Carlos Ortega, president of the one-million member Confederation of
  Venezuelan Workers, after meeting with Carter.

  Carter asked opposition and government representatives to suggest names of prominent Venezuelans who could mediate in talks, according to church
  and labor officials who met with him.

  Ortega, whose organization is threatening a general strike, said he told Carter that few Venezuelans were neutral enough.

  MORE POSITIVE VIEW

  Media owners were more positive after meeting with Carter.

  Marcel Garnier, director of Radio Caracas Television, said Carter was understanding of opposition concerns.

  Those include: an increasing number of neighborhood groups some say are armed to intimidate dissenters; a judicial system widely controlled by Chávez
  allies; and economic mismanagement.

  Chávez dismisses his critics as a privileged minority resentful of his efforts to redistribute the country's vast oil wealth.