Wall Street's main trade group on Monday threw its support behind plans by NYSE Euronext to reinstate the exchange operator's internal safeguards against volatile stock moves in the wake of recent violent swings seen around the opening and closing bells.

The Securities Industry and Financial Markets Association, or Sifma, said in a letter to regulators that allowing the NYSE to reintroduce its system could mitigate early- and late-session stocks swings until new system-wide rules take full effect later this summer.