Messi has been linked to Inter since Moratti said the record six-time Ballon d'Or winner joining the Serie A club was not a "forbidden dream".
Barca superstar Messi is contracted to the LaLiga champions until 2021 but his future is far from certain at Camp Nou, where he has clashed with board members this season.
"Messi is everyone's dream, but he won't move from Barcelona. He's still the best player there is," Moratti told Gr Parlamento.
Inter forward Martinez has been tipped to link up with Argentina team-mate Messi at Barcelona.
Also linked to Spanish giants Real Madrid and Premier League powerhouse Manchester City, Martinez had scored 16 goals in 31 games across all competitions before the coronavirus pandemic brought sport to a standstill.
"It will all depend on him, I read that Barcelona are making exorbitant offers for him which will be difficult to say no to," Moratti said.
Inter backed new head coach Antonio Conte in the transfer market at the start of the 2019-20 season and the Italian outfit are being linked with more moves.
Conte's Inter are reportedly favourites to sign Brescia and Italy sensation Sandro Tonali.
"Sandro Tonali is good but Inter already have Stefano Sensi," Moratti added.
Moratti was also asked about Inter possibly targeting Borussia Dortmund star Erling Haaland, who has taken the Bundesliga by storm since arriving from Salzburg in January.
"What he does makes you want to sign him but Inter already have Romelu Lukaku," he said.