But Atletico angered Racing by putting Martinez through medical examinations that had not been agreed to by his club, and negotiations subsequently stalled.
Inter took full advantage and Blanco revealed his expectation of Martinez moving to San Siro during an interview at the start of February.
And now an agreement is said to be close, with the striker – who has scored two hat-tricks in his last five games across all competitions – set to link up with compatriots Mauro Icardi and Lisandro Lopez in a deal reported to be worth in excess of €22million.
"It's 90 per cent complete," Blanco said on Radio Rivadavia.
"There is already a pre-agreement signed with Inter. He will leave for a sum which we believe corresponds to his value.
"I can see him going to the World Cup, even if it's ultimately up to [Argentina coach Jorge] Sampaoli to decide.
"Whenever he [Sampaoli] comes to see him, Lautaro is a real star. He has an unusual maturity for his age."
Inter are currently wrapped up in a fight to win a Champions League spot for next season, with the club sitting fourth in the Serie A table and having won just twice in their last eight outings.
The road ahead is also a tough one, with crucial clashes against red-hot Milan and league leaders Napoli next up.