Wales host Canada on 3 July and have two Test matches against Argentina on 10 and 17 July.
Phillips says the governing body hopes for confirmation on crowd numbers on 7 June.
"My hope is we can get to 10,000. What I've heard is it will probably be the lower of 25% or 10,000," said Phillips.
The Welsh government has approved pilot events to test the impact of Covid-19 on returning crowds, including football matches.
No Welsh rugby teams have so far been included among those events with Wales' four rugby regions also awaiting developments.
