LONDON (AP) — Businesses around the world are using the United States as an excuse to avoid doing business with Iran, U.S. Secretary of State John Kerry said Tuesday as he declared the Islamic Republic "open for business" for European banks.

Kerry, ahead of a meeting on Iran with European bankers, said it was unfair and inaccurate for businesses to blame U.S. sanctions for their decision to stay away. He said the U.S. had an obligation to live up to the nuclear deal with Iran by clarifying what's now permitted as a result of that accord.

"If they don't want to do business or they don't see a good business deal, they shouldn't say, 'Oh, we can't do it because of the United States,'" Kerry told reporters in London. "We sometimes get used as an excuse in this process."

The top U.S. diplomat's comments came as the U.S. works to address Iran's complaints that it hasn't received the sanctions relief it was promised in exchange for rolling back its nuclear program. Under the deal, broad U.S. sanctions on Iran's economy were removed, clearing the way for foreign companies to do business with most Iranian companies.

Yet some specific Iranian entities, including companies associated with Iran's Revolutionary Guard, are still off-limits under sanctions punishing Iran for other behavior. And the U.S. maintains a prohibition on Iran accessing the American financial system or directly conducting transactions in U.S. dollars, fueling confusion and practical impediments given that international transactions routinely cross through the U.S. banking system.

"It's just not as complicated as some people think," said Kerry, who planned to discuss the concerns Thursday with top European bankers in the U.K. He said banks in Europe were free to open accounts for Iran, fund programs and lend money. "That's absolutely open for business as long as it's not a designated entity, period. Very simple."

Asian and European government and companies, primarily banks, have sought written clarification about what current U.S. laws and financial regulations allow. Essentially, they want a promise that the U.S. will not prosecute or punish them for transactions involving Iran — a step the U.S. has so far been reluctant to take.

Meanwhile, U.S. officials have suggested that some foreign companies have other reasons for avoiding Iran, including the country's antiquated financial system that fails to meet modern international standards, as well as Iranian support for terrorism and human rights violations.

Yet foreign companies have cited legitimate concerns about potential punishment from the U.S. if they violate the remaining sanctions. In 2014, before the nuclear deal, French bank BNP Paribas agreed to pay almost $9 billion in penalties and plead guilty to processing transactions for clients in Iran and other U.S.-sanctioned nations.

What's more, foreign companies are unsure whether President Barack Obama's nuclear deal with Iran will survive. Although the Democratic candidates for president support the deal, Republicans have lambasted it and threatened to slap back sanctions after Obama leaves office.

"I just don't believe that a new president, regardless, is going to suddenly say, 'Let's go have a war in the Middle East and give up the restraint on a nuclear weapon,'" Kerry said, reprising Obama's argument that opponents of the nuclear deal are by default advocating war with Iran.

Still, the Obama administration's efforts to provide assurances about doing business with Iran have stoked outrage from Republicans and some Democratic opponents of the deal, who argue the U.S. should not be advocating economically for a country still designated by the U.S. as a state sponsor of terrorism. In recent weeks, top officials from the Treasury Department and the State Department have fanned out across the globe to explain to foreign countries and companies what's permissible under the deal.

Kerry said that as the chief architect of the sanctions and key player in brokering the deal, the U.S. had an obligation to carry out the agreement dutifully.

"Iran has a right to the benefits of the agreement they signed up to," Kerry said. "If people by confusion or misinterpretation or in some cases disinformation are being misled, it's appropriate for us to try to clarify that."

AP Diplomatic Writer Matthew Lee in Washington contributed to this report.

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