President George W Bush opens a diplomatic foray in Latin America on Friday facing a wall of public skepticism and a competing tour by his anti-US nemesis Venezuelan President Hugo Chavez.
Protests against Bush turned violent before his arrival in Sao Paulo late on Thursday for talks with President Luiz Inacio Lula da Silva, seen by Washington as a counterweight to Chavez and his push for a Latin America-wide socialist revolution.
Bush, on the first leg of a five-nation trip, is seeking to improve his standing and overcome a sense of US neglect in a region where Chavez increasingly is using Venezuela's oil wealth to court a new generation of leftist leaders.
Washington's main foreign policy focus has been on the war in Iraq, a conflict that has made Bush even more unpopular in Latin America and the rest of the world than he is at home.
Trying to blunt Chavez's challenge, Bush seems to have taken a page from the outspoken Venezuelan populist.
He suddenly is seeking to remake himself as a social reformer committed to alleviating poverty and inequality in the region.
"It's nothing more than to say we want to be your friends," Bush told RCN TV of Colombia, where he visits on Sunday.
"My trip is a chance to tell the people ... that the United States cares deeply about the human condition."
Amid rising anti-US sentiment, few Latin Americans are likely to buy such a transformation. Bush has been criticised for ignoring social ills while stressing US priorities such as free trade, drug enforcement and immigration controls.
Keeping up his anti-Bush campaign, Chavez will address a leftist rally in an Argentine soccer stadium across the River Plate from Montevideo when the US leader is due to arrive there for a state visit late on Friday.
Chavez, who called Bush the devil in a UN speech last year, will then fly to Bolivia to visit flood-ravaged areas on Saturday before Bush heads for Bogota.
Under heavy security, riot police in Sao Paulo fired tear gas and clubbed some demonstrators during mostly peaceful street protests that drew 6,000 people before Bush's arrival.
Protesters demanded an end to the Iraq war, branded Bush a planet polluter and opposed his push for a US-Brazilian ethanol deal expected to be the centerpiece of his visit.
At an anti-Bush protest in Colombia, hundreds of students tossed rocks and small explosives at riot police, who responded with a barrage of tear gas and water cannons.
Colombia's police chief said leftist guerrillas planned attacks and sabotage during Bush's visit there.
Although the White House denies it, analysts look at Bush's trip as an attempt to counter Chavez's regional sway.
Bush begins his trip by reaching out to moderate leftists like Lula and ends with conservative allies in Guatemala and Mexico.
Brazil and the United States, which together produce 70 percent of the world's ethanol, will sign a deal on Friday to share ethanol technology and help expand production in Central America and the Caribbean, the White House said.
USofficials hope "ethanol diplomacy" will limit the appeal of Chavez, who has used Venezuela's petrodollars to woo leftist allies in countries such as Bolivia and Ecuador.
But it is marred by Brazil's complaints over US tariffs on its ethanol, something the White House says is up to Congress.