(Bloomberg) — Attacks on two oil tankers near the entrance to the Persian Gulf on Thursday raised fears the strategic region could be headed toward a military confrontation between the U.S. and Iran, despite fervent mediation efforts by Japan, Germany, and the European Union.

1. What are the recent frictions about?

President Donald Trump pulled the U.S. out of the multiparty 2015 nuclear deal in May 2018 and reimposed sanctions on Iran — pressuring it to end its missile program and support for proxy militias. Tensions spiked after the U.S. ended sanctions waivers early last month that had allowed some major importers, including Japan, to continue buying Iranian oil. If prevented from using the Strait of Hormuz, Iran has warned it may close the waterway that accounts for about 40% of the world’s seaborne oil shipments.

The latest attacks followed the sabotage of four oil tankers off the coast of the United Arab Emirates last month. Back then, the attackers deployed naval mines in a manner that would do damage but not risk a major explosion of the vessels, according to a probe by the U.A.E.

2. Who is behind Thursday’s attacks?

No one has claimed responsibility for the attacks but the U.S. and its allies will undoubtedly point the finger at Iran, said Fawaz A. Gerges, professor of Middle Eastern politics at the London School of Economics.

Iran’s foreign minister, Mohammad Javad Zarif, pointed to the “suspicious” timing of the attacks on the day Japanese Prime Minister Shinzo Abe met Iran’s Supreme Leader Ayatollah Ali Khamenei in an effort to restore calm. An Iranian government spokesman also cautioned countries in the region “not to fall into the trap of some who profit from instability in the region.”

The U.S. accused Iran of being behind last month’s sabotage of four ships though it did not provide proof. U.S. National Security Adviser John Bolton said the naval mines used almost certainly came from Iran.

A joint probe by the U.A.E., Norway and Saudi Arabia unveiled on June 7 put the blame for the sabotage on a “state actor” without naming the country.

3. Will these attacks derail diplomatic efforts?

The attack on Thursday casts a pall over diplomatic efforts to avert conflict. It comes in the week that has seen German Foreign Minister Heiko Maas visit Tehran followed quickly by Abe. Iran’s supreme leader has already dismissed Trump’s calls for talks, telling Abe that Iran has no confidence the U.S. would stand by its commitments.

Efforts to quell tensions include a tour of the Gulf by the secretary general of the European Union’s diplomatic service, Helga Schmid, who started with a June 12 visit to the U.A.E. and will continue with stops in Oman, Qatar and Iran.

4. Is the region headed for war?

It’s hard to tell. Trump has insisted he isn’t looking for conflict although he said the possibility can’t be discounted.

After May’s attacks, he ordered the deployment of about 1,500 additional U.S. troops and his national security adviser warned Iran and its proxies that they “risk a very strong response” if they attacked U.S. interest in the region. The Trump administration, which has also deployed an aircraft carrier to the region, said it was evaluating the reports and would “continue to assess the situation.”

“It will take a few days to see if the U.S. just decides to send more forces to the Strait of Hormuz or if it finds a way to retaliate,” said Ryan Bohl, an analyst at Stratfor. Few are expecting a full-scale invasion of Iran at this point though the U.S., which bases its Fifth Fleet in the Gulf island of Bahrain, may consider a more limited response.

The U.A.E.’s government has stressed the importance of restraint. Its minister of state for foreign affairs, Anwar Gargash, struck a cautious tone in May, saying his country won’t be “baited” into crisis with Iran.