By Louis Charbonneau
UNITED NATIONS (Reuters) - Four leading European foreign policy officials on Thursday warned that new sanctions legislation against Iran could torpedo efforts to secure a long-term agreement with Tehran to curb its nuclear program.
The plea, in an opinion piece published in the Washington Post, appeared to be directed at the Republican-controlled U.S. Congress weighing new sanctions, even though the piece did not explicitly mention U.S. lawmakers.
It was by British Foreign Secretary Philip Hammond, French Foreign Minister Laurent Fabius, German Foreign Minister Frank-Walter Steinmeier and European Union foreign policy chief Federica Mogherini.
Some prominent U.S. lawmakers are calling for new sanctions to further pressure Iran to compromise in deadlocked nuclear negotiations with six world powers. That would be a mistake, the Europeans cautioned.
"Introducing new hurdles at this critical stage of the negotiations, including through additional nuclear-related sanctions legislation on Iran, would jeopardize our efforts at a critical juncture," they wrote.
"While many Iranians know how much they stand to gain by overcoming isolation and engaging with the world, there are also those in Tehran who oppose any nuclear deal," the ministers said. "We should not give them new arguments."
Negotiators from Iran and six major powers - the United States, Britain, France, Germany, Russia and China - failed to meet a self-imposed deadline in November for an agreement seen as crucial to reducing the risk of a wider Middle East war.
A deal would curb Iran's nuclear program in exchange for relief from economic sanctions. The new deadline for a long-term agreement is June 30.
"New sanctions at this moment might also fracture the international coalition that has made sanctions so effective so far," the Europeans said. "Rather than strengthening our negotiating position, new sanctions legislation at this point would set us back."
"For the first time ... we may have a real chance to resolve one of the world's long-standing security threats — and the chance to do it peacefully," they wrote. "We can't let that chance pass us by or do anything to derail our progress."
U.S. and Iranian negotiators will hold talks about Iran's nuclear program in Switzerland on Friday and Saturday.
Under a November 2013 accord with the six, Iran halted its most sensitive nuclear activity in exchange for some easing of sanctions. Tehran says its atomic program is peaceful but the West fears it is aimed at developing the capability to produce nuclear weapons.
(Reporting by Louis Charbonneau; Editing by Howard Goller)