Estrada, who turned 67, wants rival opposition candidates Sen. Panfilo Lacson and actor Fernando Poe Jr. "to unite for the good of the Filipino people."
"Both are my good friends and I am sure they will listen to an old friend like myself," he said.
Estrada had previously endorsed Poe, a fellow actor-turned-politician, but Lacson, Estrada’s former national police chief, refused to give way and launched a breakaway campaign.
Having topped most opinion polls after he declared his intention last year to run for president, Poe now trails President Arroyo by three percentage points in the latest survey, while support for Lacson has languished at 10 percent.
It was a battle of birthday celebrants as Presidential Spokesman Ignacio Bunye also marked his birthday yesterday, and expressed his own wish for the "best woman presidential candidate" to win.
"I think (Estrada’s) birthday wish would not be fulfilled because we are seeing indications of the strength of our President," said Bunye, who turned 59.
Sen. Robert Barbers was a bit less frivolous in his birthday greetings, as he called on the former president to "use his influence" not just to unify the opposition but the entire nation as well.
"Estrada can help unify, not just the opposition, but the entire Filipino nation as well. On this 67th birthday, I wish him all the happiness and may he continue to touch the lives of the Filipino people whom he has served in his more than 40 years of public service," he said.
Estrada received well-wishers yesterday in his resthouse in Tanay, Rizal, where he had been granted 12 hours to celebrate his birthday by the Sandiganbayan.
Estrada left his detention cell at Camp Capinpin at 9 am and headed for his resthouse less than a kilometer away.
He was entertaining some 100 supporters that had waited for him at the gate of his resthouse when he was "ambushed" by reporters.
When asked about his birthday wish, Estrada answered that he wanted Poe and Lacson to unite to improve the opposition’s chances of unseating Mrs. Arroyo.
Before reporters could ask a follow-up question, Estrada — who had been banned from talking to the media during his birthday — was whisked inside his villa by security escorts from the Police Security and Protection Office (PSPO).
Earlier on Sunday, Estrada recorded a message in Filipino that called on his supporters to vote Mrs. Arroyo out of office.
"Render your judgment on this illegal regime, which wrestled power from the nation when it forcibly ousted me from the presidency, by solidly supporting the opposition ticket," he said in his message.
The recording was smuggled out of his detention center and has been played back at opposition campaign rallies.
Estrada was toppled from the presidency in a military-backed popular revolt that swept then vice president Gloria Arroyo to power in January 2001.
Despite a Supreme Court ruling that upheld her unconventional succession, Estrada maintains that Mrs. Arroyo usurped his office.
Estrada, who faces life in prison or the death penalty if found guilty of charges of massive corruption during his 30 months in office, remains an important rallying point of the opposition.
Meanwhile, the head of the prosecution in Estrada’s trial urged his allies in Congress to introduce a law that would allow high-profile inmates to enjoy house arrest.
"It’s about time people who have been advocating house arrest should translate their efforts into proposing a law that would allow house arrest under special conditions," Chief Special Prosecutor Dennis Villa Ignacio told reporters.
Prosecutors and defense lawyers are at loggerheads over the issue of Estrada’s detention at his resthouse.
The government argues Estrada’s detention in his resthouse would be illegal because no law allows it, while the defense argues that such detention is an option for the court because no specific law forbids it.
In the absence of a law on house arrest, Villa Ignacio pointed out that the anti-graft court "doesn’t know how to act and the prosecution would always argue that there is no law allowing such privilege."
Defense lawyer Jose Flaminiano invoked "charity" for the Sandiganbayan to reverse two previous rulings that turned down Estada’s "resthouse" arrest proposal, noting that Estrada as a former head of state is a "class in himself."
He said that the inspection of Estrada’s sprawling Tanay property by Justices Minita Chico-Nazario, Edilberto Sandoval and Teresita Leonardo-de Castro was a sign that the anti-graft court was sympathetic to their request.
But Villa Ignacio disagreed, saying that charity and compassion should not get in the way of justice.
"They are outside the provisions of the law. Courts act on incidents based on what the law and procedure dictates. There will be no justice if compassion gets in," he said
Villa Ignacio expressed doubts over Estrada’s complaints over the conditions of his confinement at Camp Capinpin, such as the purported absence of water.
"Water is a priority item in a military camp. If there is a problem like that, it may be reflective of the incompetence of the camp commander," he said. - With Marichu Villanueva, Jose Rodel Clapano, AFP, AP