Mexican side Leon defeated Los Angeles FC 2-1 to take a slender advantage after the first leg of the CONCACAF Champions League final on Wednesday.

First-half goals from Colombian international William Tesillo and Ecuador forward Angel Mena looked to have secured Leon a comfortable victory at the Estadio Leon.

But the Liga-MX side's hopes of winning the continental title for the first time were jolted after Los Angeles forward Denis Bouanga scored in the sixth minute of second-half stoppage time to hand the Major League Soccer champions a crucial lifeline.

Los Angeles went into the first leg with high hopes of emulating last year's champions Seattle, who became only the second MLS team to ever be crowned champions of CONCACAF, the regional grouping for teams from North America, Central America and the Caribbean.

However the California club were given a footballing lesson for long periods by an incisive Leon team who had not played since a May 7 defeat to San Luis in Liga-MX.

Leon dominated the first half with the movement of their front line, led by Jose Alvarado and Victor Davila, repeatedly exposing Los Angeles down the flanks.

Alvarado nearly fired Leon into the lead after seven minutes, with only a diving fingertip save from LAFC goalkeeper John McCarthy denying the home side an opening goal.

Leon did not have to wait long for the opener however, with the Mexicans taking the lead from the corner following McCarthy’s save.

Mena's outswinging setpiece was met by left-back Tesillo, whose angled header flew in off the post to make it 1-0.

Los Angeles almost got back into the game in the 36th minute, but a promising counter-attack broke down when Jose Cifuentes misdirected his pass into the penalty area behind advancing team-mate Kwadwo Opoku.

That wasted opportunity was emblematic of LAFC's first-half performance, when all too often their forays into Leon territory broke down due to inaccurate passing.

Leon's hopes were then given a huge boost in stoppage time at the end of the first half, when defender Jaine Barreiro's header from a corner was adjudged to have just grazed LAFC fullback Ryan Hollingshead's forearm.

Referee Walter Lopez initially gave a corner, but after a review by VAR the Guatemalan official pointed to the spot to roars of delight from the home crowd.

Mena duly stepped up to hammer home the spot-kick to leave Leon 2-0 up at half-time.

Los Angeles rallied briefly early in the second half, but again failed to seriously test Leon goalkeeper Rodolfo Cota.

Instead it was Leon who looked the likelier to score, with only LAFC goalkeeper McCarthy keeping the tie alive with a string of fine saves, including one remarkable 58th minute block to deny Mena from close range.

Leon looked to have killed the tie off in the closing stages but had a goal disallowed.

Instead Los Angeles finally conjured a breakthrough in the dying seconds, when Bouanga prodded home Mateusz Bogusz's cross.