As address to U.S. Congress nears, Netanyahu treads a thinning line

Israel's Prime Minister Benjamin Netanyahu gestures while he speaks to supporters of his Likud party as he campaigns in the West Bank Jewish settlement of Maale Adumim, near Jerusalem February 25, 2015. REUTERS/Nir Elias

JERUSALEM (Reuters) - When Prime Minister Benjamin Netanyahu accepted an invitation to address the U.S. Congress two weeks before an Israeli election, there appeared to be little downside. As the appointment draws near, the potential pitfalls are growing.

The primary objective was to warn U.S. lawmakers about the risks of a deal on Iran's nuclear programme and keep alive the possibility of further sanctions on Tehran, frustrating President Barack Obama's long-running policy of negotiation with the Islamic Republic.