Venezuelan President Hugo Chavez sang, danced and said he intends to stay in power for two more decades as he celebrated his 57th birthday looking ahead to months of cancer treatment. Chavez rallied a crowd of cheering supporters from the balcony of the presidential palace on Thursday, waving a large Venezuelan flag and briefly wrapping himself in it. He said he expects to lose his hair soon as a result of chemotherapy and that a long process of treatment lies ahead. This is going to be various months all of this year, but I'm going to continue in charge of my government functions," Chavez said. He mixed serious statements about his upcoming treatment with the ecstatic rallying cries of a leader already in pre-campaign mode ahead of the 2012 election. "Next year, we will win the presidential elections once again! Strength, unity!" Chavez said. Setting a goal he has never before reached, he said: "We're going for 10 million votes next year!" The crowd chanted: "Oh, no! Chavez won't go!" Chavez sang and danced briefly with one his daughters on the balcony while a band below played folk music. He saluted to the crowd and blew kisses, standing next to three grandchildren. His supporters sang while atop a giant birthday cake sparkling candles burned. I invite you all to celebrate my 77th," Chavez said. "I had said I'd leave in 2021. Well, I'm not going away in 2021 or anything. Maybe in 2031." The leftist leader has been in office since 1999 and is seeking re-election next year to another six-year term. A poll released last week said Chavez's public approval rating remains at 50 percent and hasn't significantly varied since his cancer diagnosis. Chavez underwent surgery in Cuba on June 20 to remove a cancerous tumor. He hasn't said what type of cance r he has been diagnosed with or specified where exactly it was located, saying only that it was in his pelvic region. He underwent his first phase of chemotherapy in Cuba last week and said the treatment aims to ensure that no malignant cells reappear. "Soon surely my hair will start to fall out - inevitable," Chavez said. "They will apply new doses of chemotherapy in the coming days." When patients undergo such surgery to remove a tumor, "there's always a concern of microscopic cells, or individual cells left behind even though all of the physical tumor is removed," said Dr. Jeffrey Crawford, chief of medical oncology at Duke University Medical Center in Durham, North Carolina. The role of chemotherapy is to go through the body and attack any remaining cells that may have been laying dormant or hidden," said Crawford, who is not involved in the president's treatment. Crawford said it's not possible to draw conclusions about Chavez's treatment based on the president's account that his hair will fall out because that's often the case with many chemotherapy regimes. But based on Chavez's comments, he added, "I think the best-case scenario would probably be three to four months of c hemo. Chavez said he should be finished with the most difficult phases of his treatment by December, when he hopes to host a summit of Latin American leaders in Caracas. "At the end of the year, I should have passed this hard, careful, very, very strict phase," Chavez said in a telephone conversation aired on television Thursday morning. He said he sent letters inviting Latin American and Caribbean leaders to the summit in Caracas on Dec. 9. That meeting had originally been scheduled for July 5-6 but was postponed due to Chavez's illness. Around the country, the president's supporters held a series of televised events honoring his birthday. A group of children sang for him, oil workers in red hardhats wished him the best and the president's older brother, Adan, led a crowd in their home state of Barinas singing "Happy Birthday. Chavez made his only public appearance of the day at the presidential palace. He said that for now he needs to limit his contact with the public because his white blood cell count has declined as a result of chemotherapy, lowering his natural immune defenses. "I'd like to be down there with you all, but I shouldn't," Chavez told his audience from the balcony. I have to take a great deal of care." Still, he assured his supporters, "I feel that I'm being reborn. I'm starting a new life." Turning to politics, Chavez denounced his adversaries as "los escualidos," or the squalid ones. He said some of his opponents have been "going around now with the tale that this is a show, that I don't have anything."-