The Premier League has been suspended since March 13 amid the COVID-19 crisis and June 12 has been identified as a possible date to restart. Players returned to training in small groups this week.
Among the top European leagues only the Bundesliga has resumed.
"We've taken the first step," Masters told BBC Sport.
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"It's great for everybody, including the fans, to see our players back on the training ground."
Masters said that the Premier League remains flexible on the date of resumption, contingency plans were needed and "curtailment" was still an option.
"We wouldn't have taken the first step to get back to training if we weren't convinced we had created a very safe environment for our players," he said.
"It is the first step and we have to be sure when we go to contact training we have completed those processes.
"We have done everything we possibly can to make return to training as safe as possible," he added.
"We think it is safe to return. We have to respect players' decisions not to return to training. I would be comfortable to return to training."
Liverpool are top of the table with a 25-point lead over Manchester City.
Culture Secretary Oliver Dowden said on Wednesday that the return of contact training in elite sports could get government approval "later this week". (Reporting by Julien Pretot; Editing by Toby Davis)
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