NEW YORK (Reuters) - Planned talks this week between Iran and six world powers, including the United States, will show how serious Tehran is about resolving issues around its nuclear program, a senior State Department official said on Monday.

"In all the meetings with the Europeans, there was a clear sense that this opportunity with the Iranian foreign minister will give our ministers a sense of their level of seriousness and whether they are coming with concrete new proposals and whether this charm offensive actually has substance (under it)," a senior U.S. State Department official told reporters.

The official was referring to U.S. Secretary of State John Kerry's meetings with European counterparts, including British Foreign Secretary William Hague on Monday.

(Reporting by Arshad Mohammed; Editing by Sandra Maler)