Move meant to ensure that Tehran sees the relief that the U.S. and others pledged it in January.

LONDON—U.S. Secretary of State John Kerry met with heads of some of Europe’s biggest banks in London on Thursday to address their concerns about doing business in Iran, in a controversial push to ensure that Tehran sees the relief that the U.S. and other world powers pledged it in a nuclear accord that took effect in January.

After a roughly hour long meeting, Mr. Kerry said he hoped to glean from bankers the obstacles they see to doing business with Iran and to address them.

“We want to make it clear that legitimate business, which is clear under the definition of the agreement, is available to banks as long as they do their normal due diligence and know who they’re dealing with,” Mr. Kerry told reporters. “They’re not going to be held to some undefined and inappropriate standard.”

Mr. Kerry and other U.S. officials have crisscrossed the globe in recent weeks in an effort to meet with banking and business leaders to promote investment in Iran, a country with which the U.S. has no diplomatic ties. But many European banks have been wary of doing business involving Iran while U.S. sanctions are still in place and a ban remains on dollar-denominated transactions.

“They [the Iranians] have an expectation that the sanctions that are supposed to be lifted are in fact lifted.” Mr. Kerry said Thursday.

British Foreign Secretary Philip Hammond said the U.S., U.K and other world powers that negotiated the deal were actively working “to support European businesses in resuming normal trade and investment patterns with Iran.”

Mr. Hammond, who also attended the meeting of about 10 banking representatives as well as British officials and officials from the U.S. Treasury and state departments, said that allowing Iran access to the global financial system was key to the nuclear agreement’s success. The banking officials met for another hour after Mr. Kerry and Mr. Hammond left the meeting to attend an anti-corruption summit.

“It’s the first hurdle in the race,” Mr. Hammond told reporters, speaking alongside Mr. Kerry. “If we fall at this one we’ll never get the chance to demonstrate all the other benefits that can flow from this agreement that we spent so much time and energy delivering.”

Top bankers at the meeting on Thursday included John Cryan, chief executive of Deutsche Bank AG, and António Simões, chief executive of HSBC Bank PLC, part of HSBC Holdings PLC. Other attendees included Tracy Clarke, regional chief executive for Europe and Americas at Standard Chartered PLC and Michael Roemer, group head of compliance at Barclays PLC.

British Bankers’ Association Chief Executive Anthony Browne, who also attended, is helping to coordinate banks’ views and concerns on Iran business.

A U.S. official said Mr. Kerry told the bankers he’s aware that Iran hasn’t done anything to lessen banks’ concerns about doing business in the country.

“He specifically mentioned our acknowledgment that Iran, despite the fact that they’re meeting their obligations in the [nuclear accord], continues to conduct destabilizing support for terrorists, ballistic-missile activity,” the official said. “They continue to provoke and to destabilize the region in other unhelpful ways and we understand that that is also causing a measure of skittishness.”

The meeting also touched upon bankers’ concerns about the potential consequences of taking on new Iranian business if the U.S. stance on Iran changes, a person familiar with the matter said. A further meeting between banks and U.S. officials is to be held in Washington, D.C. next week, the person said.

Some banks say that they have made up their minds on not doing business with Iran, in part because they have agreements in place with U.S. agencies that may take a different view than the official government stance on Iran.

“We were happy to share the practical and legal considerations behind our stated position on Iran with the secretary of state and the foreign secretary at the meeting today: we won’t accept any new clients who reside in Iran, or which are an entity owned or controlled by a person there, nor will we undertake any new transactions involving Iran or any party in Iran,” a Standard Chartered spokesman said.

Standard Chartered settled previous allegations over its dealings with Iran with U.S. authorities in 2012 but has said that it faces a new fine over additional alleged activities that took place while Iran was still under sanctions.

Deutsche Bank said it continues to generally restrict business connected to Iran.

HSBC too has shunned business with Iran to meet its pledge to follow U.S. standards on sanctions and anti-money laundering as part of its 2012 deferred prosecution agreement with the Department of Justice. It previously admitted to carrying out illegal transactions with customers in Iran.

By Felicia Schwartz & Margot Patrick