* Mexico's AMLO says energy policies do not violate USMCA
* U.S. delegation heads to Colombia to meet Petro
* Lula skips party convention as he secures nomination
* Colombian gangs propose ceasefire
July 21 (Reuters) - The latest in Latin American politics today:
Pressure mounts on Peru's Castillo
Peru's Attorney General Patricia Benavides opened a new probe of President Pedro Castillo, a day after the country's former interior minister accused the leftist leader of obstructing graft investigations of close allies, prosecutors said on Thursday.
The investigation was triggered by Castillo's abrupt firing on Tuesday of Mariano Gonzalez, who had served as interior minister for two weeks. The firing followed Gonzalez's decision to authorize the appointment of a special police unit meant to track down and arrest allies of the president who are under criminal investigation.
Presidents in Peru have immunity and cannot be indicted by the courts during their five-year term, but they can be investigated. Benavides in May opened an investigation into Castillo over alleged influence peddling, collusion and being part of a "criminal organization."
Mexico defends energy policy amid dispute
Mexican President Andres Manuel Lopez Obrador on Thursday denied his energy policies breached a regional trade agreement, responding to news that Canada had joined a U.S. demand for dispute settlement talks over his energy agenda.
Lopez Obrador said at a regular news conference that Mexico would defend control of its oil as well as its power market policies, and that there had been "no violation" of the USMCA trade pact.
U.S. open to discussing Colombia trade deal with next president
A senior U.S. official said the Biden administration is willing to discuss the existing U.S.-Colombia trade agreement with Colombia's incoming president, Gustavo Petro, ahead of a high-level delegation dispatched to Colombia on Thursday.
The delegation will meet with outgoing President Ivan Duque as well as Petro, who takes office Aug. 7.
The visit is intended to calm "speculation" about the U.S.-Colombia relationship, one official said, referring to questions about how well the two countries would work together once Petro takes office.
Lula gets party's official nomination as election nears
Former Brazilian President Luiz Inacio Lula da Silva was officially nominated by his Workers Party (PT) on Thursday to run on Oct. 2 against far-right incumbent President Jair Bolsonaro in Brazil's most polarized election in decades.
Lula did not attend his party's convention in Sao Paulo, instead taking to the campaign trail and meeting with voters in his home state of Pernambuco in impoverished northeastern Brazil.
"He said that's enough of inside party talk; it's time to go to the streets and talk to voters," a Lula aide told Reuters.
Colombian illegal armed groups propose ceasefire with incoming government Six of Colombia's top criminal gangs, who are linked to producing and trafficking cocaine, proposed a ceasefire to incoming leftist President Petro as a starting point for peace talks.
The illegal armed groups, which included the Clan del Golfo, the Caparros, and the Rastrojos, sought guarantees equal to those obtained by others that previously disarmed through peace agreements, in addition to suspending the extradition of people who are committed to any potential peace process.
Uruguayan president says wants China trade deal with or without Mercosur
Uruguayan President Luis Lacalle Pou told fellow members of the South American Mercosur trade bloc that his country will push toward a free-trade deal with China with or without their assent.
Soon after Argentine President Alberto Fernandez, speaking at the trade bloc's first in-person meeting since the pandemic, urged fellow members to do a joint deal with China, Lacalle Pou said his country would proceed with country-on-country talks with the Asian giant in the next few days.
"We will consult with the other Mercosur members and invite them to join but if they say no, Uruguay will go ahead," he said. (Compiled by Brendan O'Boyle Editing by Alistair Bell)