Such a ruling could mean that a verdict could come before the February vote.
Berlusconi's lawyers also decided not to call the Moroccan woman at the centre of the case, Karima el-Mahroug, to testify, saying her testimony would have "interfered with the serenity of the electoral campaign".
But they asked to hear from six more witnesses instead, including actor George Clooney, who has said he visited the premier's residence once. El-Mahroug, better known as Ruby, had appeared in court on Monday ready to testify after having failed to show on two previous dates, purportedly because she was in Mexico on vacation.
Berlusconi is accused of paying for sex with the 20-year-old when she was 17 during his notorious "bunga bunga" parties – racy soirees at his villas in which dozens of young women were present – and then using his office to cover it up.
Both deny sexual contact. Berlusconi has apologised for hosting the parties, saying he was lonely after splitting from his second wife. Veronica Laria left him in 2009, citing alleged dalliances with young women.
Berlusconi attorney Niccolo Ghedini had filed a motion to suspend the proceeding, citing the demands of Italy's election campaign. The prosecution opposed the request, arguing that Berlusconi was neither the formal head of his party nor its official candidate for premier, and that he has infrequently shown up for trail anyway, as is his right.
'Bunga-bunga'
In their ruling, the judges said Berlusconi's absences for a political campaign were a personal choice and couldn't be compared with having a parliamentary obligation – which has been accepted as a legitimate reason to delay a trial.
Ghedini said that in allowing the trial to go ahead, it was clear the court wanted to see a verdict before the February 24-25 election. "It doesn't bother us at all. It should bother the citizens because it is obvious that this will impact the electoral campaign," he told reporters. Berlusconi has long accused Milan magistrates of mounting politically inspired cases against him – a charge they deny.
Prosecutors had already said they didn't need el-Mahroug's court testimony, explaining they had what they needed from other evidence already submitted. The defense had put her on its witness list, but Ghedini on Monday declined to call her.
"We would have preferred to hear her in the trial, but it is unthinkable to do something like this when the election campaign is in full swing," he said. "Our renunciation is a bitter renunciation." El-Mahroug's lawyer, Paola Boccardi, said her client wasn't angry that she didn't have to testify, just "surprised that she wasn't heard".
Ghedini, however, said he wanted to call six other witnesses on his witness list who hadn't yet been heard from, including Clooney and el-Mahroug's mother. Clooney has said he was approached by Berlusconi's team to testify about the "bunga bunga" parties, but says he only visited the premier's residence once to seek aid for Darfur and declined an invitation to stay.
The court is expected to decide on Monday on the request to hear from the additional witnesses. El-Mahroug looked relaxed, chatting with her lawyer while in court. – Sapa-AP