Reuters agency was informed by a source close to the talks, Censor.NET reports.
The two sides are meeting in San Francisco as part of talks that have dragged on for five months. They hinge on whether the bonds' face value should be written down.
Ukraine must pay a $60-million coupon on Aug. 23 and a chunkier $500-million bond maturing on Sept. 23.
Kyiv says it will halt debt payments if an agreement to reduce the face value of the debt is not reached with private creditors this week.