Bush, here on the third stop of what he calls his final Europe trip before leaving office in January, was to hold separate talks with his staunch Iraq war ally and with Pope Benedict XVI on Friday before heading to France.
No protesters — or even rude gestures — were visible from the US president's motorcade as it screamed from the airport into Rome, just hundreds of Romans snapping photos with pocket cameras or cell phones.
Bush and Berlusconi were also expected to discuss the Middle East peace process, the situation in Lebanon, and efforts to bring newly independent Kosovo closer to its European neighbours, officials on both sides said.
"I expect that the full range of issues that were covered in today's stop will also be covered: Iran, Afghanistan, Kosovo," US deputy national security adviser Judy Ansley, said after Bush met with German Chancellor Angela Merkel in Meseberg, Germany.
Bush hopes Italy will step up support for NATO-led efforts to rebuild Afghanistan and battle Islamist extremists there, she said, but "I don't know in terms of troops or assistance or what it might be."
For his part, Berlusconi was expected to seek Bush's full backing for Italy's drive to be included in negotiations with Tehran over its nuclear programme, in addition to permanent UN Security Council members Britain, China France, Russia, the United States — plus Germany.
Italy "can count on its American friends" in its bid to join the group, Foreign Minister Franco Frattini said Wednesday, adding on Italian television: "But let's wait for Bush's statements."
Armed also with France's support, Frattini said it was "unthinkable" that Germany would not drop its objections, and Italian media said Bush had pressed Merkel on the issue.
But Ansley seemed to douse Italian optimism, saying the issue would come up but that "whether they're made part of it, I don't know how realistic it is."
Berlusconi's position on Iran is close to Washington's, while his centre-left predecessor Romano Prodi advocated dialogue with Tehran.
The conservative Berlusconi established himself as one of Bush's strongest European allies in the run-up to the Iraq war in 2003, during the Italian leader's last stint as prime minister, despite massive opposition at home.
Bush, who has hosted the media tycoon both at the White House and at his Texas ranch, was making his sixth visit to Rome under tight security, with 10,000 police and soldiers deployed in the streets.
Around one thousand demonstrators, bracketed by police, protested against Bush, marching from the central Piazza della Repubblica to the US embassy, some shouting "Bush terrorist," "Bush warlord" and "Italy out of NATO."
Their banners called for a withdrawal of Western forces from Afghanistan and Lebanon.
Frattini told AFP Tuesday that Italy planned to step up its military responsiveness in Afghanistan, cutting response time for "rapid intervention" from 72 hours to a proposed five or six.
But Italy's 2,500 soldiers will remain deployed in Kabul and the relatively quiet Herat region in the west of Afghanistan, he said.
As Bush and Berlusconi meet in Rome, donors will be meeting in Paris to pledge funding for an ambitious 50 billion dollar (32 million euro) post-Taliban reconstruction plan spanning five years.
Bush, who had no public events planned Wednesday evening, was to lunch with his Italian counterpart Giorgio Napolitano on Thursday and meet with Berlusconi in the early evening before the two face reporters at about 7:30 pm (1730 GMT).
First Lady Laura Bush was to address the UN World Food Programme in the early afternoon on Thursday.
On Friday the US leader was to head to the Vatican for his second meeting with Pope Benedict XVI.
He will be treated to an audience in the mediaeval St John's Tower at the Vatican, reserved for illustrious guests, and a stroll in the Vatican Gardens.
The gesture was a response to the warm White House welcome on his 81st birthday, April 16, according to Vatican spokesman Federico Lombardi.
