Monterrey midfielder and U.S.-Mexico dual national Jonathan Gonzalez has opted to play for Mexico over the United States for his international future, sources have confirmed to ESPN FC.

The Mexican Football Federation (FMF) would not officially comment on Gonzalez's decision, but a source close to the organization said: "Everything is moving along well, but there are still some steps that need to be put in place and we need the final signature of the player.

"Jonathan has decided to continue with the process, but until the FMF has an official signature we will not declare [the move] official."

News of Gonzalez's decision was first reported by Univision, and ESPN FC confirmed through independent sources. U.S. Soccer declined to comment on Monday ahead of announcing a 30-man squad for January's training camp.

Gonzalez then tweeted on Monday night: "If I'm called [by the Mexico national team], I'm determined to defend the colors of this country. It would be an honor."

Gonzalez, 18, was born in California and has played for U.S. youth national teams from the under-14 to under-20 levels but has yet to play for the senior team despite enjoying a breakout year for his club in the Mexican league, where he helped Monterrey win the Copa MX and was named to the Liga MX Apertura Best XI.

Gonzalez has long stated his desire to play for the U.S., but after the Americans' failure to qualify for the 2018 World Cup, the FMF said it remained hopeful that Gonzalez would consider switching allegiances, which the player can do once under a FIFA rule for players who have yet to make a senior national team appearance in a competitive game.

Ahead of November's friendly in Portugal, U.S. Soccer made a decision to allow Gonzalez to stay with his club as it entered the Liga MX playoffs, as playing in the exhibition game would not have tied him to the U.S. anyway.

But Gonzalez told Soccer America last week that no one in the U.S. Soccer Federation called him to explain the omission -- something the player reportedly was not happy about.

"I wasn't called in, in November," Gonzalez said. "Personally, nobody came and talked to me and let me know about that friendly. I just wasn't called in."

Jonathan Gonzalez will play for Mexico after representing U.S. youth teams as recently as April. Hector Vivas/Getty Images

A high-ranking member of the Mexican federation traveled to California to talk to Gonzalez and his family during the winter offseason, while Mexico coach Juan Carlos Osorio recently spoke to the player on the phone to discuss a potential switch.

Gonzalez played for the U.S. under-18 team last April and was in contact with Bruce Arena before the coach's departure after the Americans' failure to qualify for the World Cup in October.

But the United States won't have a competitive fixture until the 2019 Gold Cup, while Mexico is gearing up for the 2018 World Cup over the coming months. If the paperwork is completed in time, Gonzalez could debut for El Tri in its Jan. 31 friendly against Bosnia and Herzegovina.

Thomas Rongen, U.S. Soccer's chief scout under Arena, told CBS Sports that he had been to Gonzalez's house "three times in the last year," but that the U.S.'s qualifying failure, together with the background of Gonzalez's father, proved to be too much to convince the midfielder to stay with the U.S.

"Not going to the World Cup ourselves, that has been tough. I knew going forward, we might lose some battles," Rongen said. "It's a big loss, obviously. He would have liked to play for the U.S., but you know what, his dad is so Mexican, that he wanted him to represent Mexico and I knew it was a losing battle, probably."

Osorio said in an interview that he sees Gonzalez not as a holding midfielder, where he plays for Monterrey, but instead in one of the more attacking central midfield roles in a 4-3-3 formation.

A U.S. youth international deciding to play for Mexico is unusual, though the reverse case has been more common. Most recently, FC Dallas goalkeeper Jesse Gonzalez, who played for Mexico at the under-20 and under-23 levels, filed a switch to play for the U.S. senior team last June.