"At the moment there is no consensus on new sanctions as an effective instrument," he said at the close of a two-day meeting in Italy, after British foreign minister Boris Johnson raised the issue with the Group of Seven.
"There are clearly different opinions," Alfano said, adding that the G7 had reaffirmed its support for those sanctions already in place.
Johnson on Monday raised the possibility of "further sanctions on some of the Syrian military figures and some of the Russian military figures who have been involved in coordinating the Syrian military efforts".
US Treasury Secretary Steven Mnuchin said last week that the US would soon impose additional sanctions on Syria, as part of a military, diplomatic and financial response to a chemical attack blamed on the regime.
French Foreign Minister Jean-Marc Ayrault confirmed Johnson had raised the issue on Tuesday morning but said the diplomats had not discussed the issue in any depth.
Italy's Alfano stressed that for Rome "sanctions are a tool and not an end in itself" and warned against measures that would isolate Russia and back it "into a corner".