CARACAS (Reuters) - Venezuelan opposition parties cautiously accepted an offer of dialogue from President Hugo Chavez on Sunday but said the firebrand socialist leader had soon forgotten similar invitations in the past. Chavez proffered the olive branch during a typically lengthy speech to parliament on Saturday in which he also denied being a dictator and said he might give up much-criticized decree powers a year ahead of schedule. It was Chavezs first address to a new National Assembly that began work this month with a greater number of opposition members. The last parliament was dominated by Chavez supporters after the opposition boycotted a legislative vote in 2005. The president often denounces his rivals as traitors and far-right pawns of Washington. But on Saturday he appeared to be in a more conciliatory mood, welcoming them to the Assembly and urging them to seize an historic opportunity. Opposition leaders tentatively welcomed the comments from Chavez but said concrete action was needed to show he was serious. Dialogue cannot be just words ... we have a president who bashes the media, churches, NGOs, other countries, fighting with everyone for 364 days a year, then for one day he says he wants dialogue, said opposition lawmaker Julio Borges. We will remind him of all the times he has called for dialogue in the past that did not result in talks. Chavez has led the South American OPEC member on an increasingly radical path since 1999 and requested decree powers from the outgoing parliament at the end of last year. Critics said that move was aimed at cynically undermining the incoming Assembly, where opposition parties had been hoping to put the brakes on his legislative agenda. Fernando Soto Rojas, a Chavez ally who is the new Assembly president, said the time was ripe for fresh political dialogue in the continents biggest crude oil producer. I believe that in todays Venezuela is it perfectly possible for all Venezuelans to co-exist, he said. Chavezs supporters say the charismatic former soldier is redressing years of inequality and that his self-styled 21st century socialism project is helping a downtrodden majority. Critics accuse him of ushering in Cuban-style communism and say he is wrecking what should be one of the regions richest economies with ill-planned policies that scare away investors, including a wave of nationalizations in recent years. Opposition lawmaker Andres Velasquez cautiously welcomed the presidents warmer tone but also pointed out that he had said the same things in the past with no result. It is not the first time he has done this ... he has repeated it many times and nothing has happened, Velasquez said. We hope the promise of dialogue can really now be made concrete.