June 27 (Reuters) - Major U.S. telecom service providers

said on Thursday some of their users traveling overseas were

having connectivity problems due to an issue at a partner

network provider.

In statements to Reuters, Verizon, AT&T ( T ) and

T-Mobile US ( TMUS ) said they were working to resolve the issue

but did not provide details on the extent of the outage or the

services partner responsible for it.

However, a person familiar with the matter said it was due

to a glitch at Syniverse, a telecom services firm that works

with global carriers to support international roaming.

In a response to Reuters, Syniverse said its systems were

facing "intermittent connectivity issues" and was working with

its network partners to fix the problem.

Verizon said 70% of its customers' calls and data

connections were currently going through, while it worked to

resolve the issue.

AT&T ( T ) said its network was operating normally and some

customers traveling overseas were experiencing disruptions "due

to an issue outside the AT&T ( T ) network".