Attacks on two oil tankers in the Gulf of Oman have sent tensions soaring between Iran and the United States, and reinforced fears that the two countries could be hurtling toward an unintended war.

With no diplomatic relations between the two countries, no serious dialogue underway despite efforts by other countries to mediate, and no letup in U.S. economic pressure on Iran, former U.S. officials, foreign diplomats and experts said there is a growing risk that a miscalculation, coupled with deep distrust, could trigger a conflict that neither side wants.

"In many ways, I feel like this is a 1914 moment for the region, that a single incident could put the entire region on fire," Ali Vaez, Iran project director at the International Crisis Group think tank, said in an apparent reference to the assassination of archduke Franz Ferdinand of Austria that ended up leading to World War I.

"Although this particular incident might not be the one to push the parties over the edge of the abyss of war, each cycle of escalation brings us closer to the brink."

Hours after the explosions, Secretary of State Mike Pompeo described the incident as a "blatant assault" and said the U.S. had concluded Iran was responsible for targeting the Norwegian-owned and Japanese-owned ships along the vital oil transit route near the strategic Strait of Hormuz. Pompeo cited intelligence reporting, recent similar incidents and the sophisticated nature of the attacks.

Pompeo said a previous attack against four ships last month off the coast of the United Arab Emirates that Washington blamed on Tehran, a drone attack on a Saudi Arabian pipeline, a rocket attack near the U.S. embassy in Baghdad and other strikes were allegedly part of a deliberate pattern of "aggression."

"Taken as a whole, these unprovoked attacks present a clear threat to international peace and security, a blatant assault on the freedom of navigation and an unacceptable campaign of escalating tension by Iran," Pompeo said.

Iran denied any role in the attacks. But Pompeo said Tehran was retaliating because of crippling U.S. economic sanctions that have slashed Iran’s oil exports and severely damaged its economy.

"Iran is lashing out because the regime wants our successful maximum pressure campaign lifted," he said.

The U.S. Central Command released video Thursday night that it said showed an Iranian Revolutionary Guard Corps patrol boat approaching one of the ships, the Kokuka Courageous, hours after the explosion and removing an unexploded mine.

The tanker attacks coincided with a spate of mixed messages from both countries, which former officials said added to the danger that each country could be misreading the other.

Although President Donald Trump has imposed punishing sanctions on Iran since pulling the U.S. out of the nuclear deal between Tehran and world powers, he has also repeatedly said he is open to talking to the country's leaders.

On Tuesday, Iran released a Lebanese businessman and U.S. legal resident who had been imprisoned since 2015, a move that the Trump administration called a "positive sign." Iran also has so far refrained from entirely abandoning the nuclear agreement it negotiated with world powers, which prohibits the regime from enriching uranium to weapons-grade levels.

But despite efforts by Japan, European and other governments to find ways to defuse the standoff between Iran and the United States, neither side so far has signaled a readiness to back off entrenched positions and make significant concessions.

In a bid to broker talks, Japanese Prime Minister Shinzo Abe paid an unusual visit to Tehran on Wednesday and said he brought with him "a message" from Trump.

But Ayatollah Ali Khamenei, the country's supreme leader, dismissed the offer. “I do not consider Trump as a person worth exchanging any message with and I have no answer for him, nor will I respond to him in the future,” Khamenei said in a statement.

The two adversaries are locked in a faceoff and the Iranian regime appears reluctant to take any step that would amount to caving in to U.S. pressure, experts said.

Retired U.S. Navy admiral James Stavridis, who served as NATO commander, said it was unlikely that Iran or the United States would climb down in the high-stakes showdown.

“We’re on a collision course here,” Stavridis, who is the chief international diplomacy and national security analyst for NBC News, told MSNBC.

Further complicating any attempt to find an “off-ramp” to the crisis is the collapse of diplomatic channels that had been forged during the talks that produced the 2015 nuclear deal. Former Secretary of State John Kerry and his Iranian counterpart Javad Zarif spoke frequently and defused at least one potential crisis in 2016 when a group of U.S. Navy sailors were captured after straying into Iranian territorial waters.

The attacks Thursday on the two oil tankers drove up oil prices and shipping companies braced for a rise in insurance costs. Two oil tanker owners, DHT Holdings and Heidmar, have suspended new bookings for the Persian Gulf, industry media reported.

No group claimed responsibility for the incident. But some former U.S. officials and lawmakers agreed with the Trump administration's assessment pointing the finger at Iran, saying Tehran had the necessary guerrilla warfare skills and a strong interest in pushing up oil prices for its own hard-hit economy.

Norman Roule, a former CIA officer who focused on Iran, said "the circumstantial evidence is vast and sufficiently significant that Iran was responsible for these attacks."

Roule predicted there would be more efforts to disrupt oil shipping routes: “We should be concerned that attacks represent the new normal for the foreseeable future in Iran’s campaign to conduct unconventional attacks to pressure the international community to push back on U.S. sanctions.”

Although Iran had an incentive to drive up oil prices, it did not appear eager for a war with the U.S, Bruce Riedel, a former career CIA officer now at the Brookings Institution, said. Some other group or government keen on provoking a conflict had to be considered a potential suspect, he said. “The possibility of a mysterious third force can’t be ruled out here.”

If Iran was indeed behind the attacks in the Gulf of Oman that sent plumes of smoke billowing into the air, it was not surprising given the degree of economic pressure bearing down on the regime, said Ilan Goldenberg, a former senior official in the Obama administration.

“This is purely a function of Trump's escalatory 'maximum pressure' campaign. You can't just keep poking someone & expect them to sit around & take it," Goldenberg, now a senior fellow at the Center for New American Security think tank, said in a tweet.

Supporters of the Trump administration said that Iran will eventually come to the negotiating table as the sanctions steadily strangle the country's economy.

Pompeo vowed that the U.S. would “defend its forces, interests and and stand with our partners and allies to safeguard global commerce and regional stability,” though he did not explicitly threaten a U.S. military response.

Republican Sen. Lindsey Graham of South Carolina, a staunch supporter of the administration's tough line on Iran, said he wanted to see Trump slap more sanctions on Iran as a result of the attacks that Pompeo blamed on Tehran.

"They need to feel pain for this escalation and additional sanctions would be the appropriate response," Graham said.

It's not clear whether the relatively small-scale strikes on foreign oil tankers are enough to prompt the president to approve military action.

Some more hard-line lawmakers and officials in the Trump administration, including national security adviser John Bolton, believe that the Iranian regime could collapse from the economic pressure caused by the U.S. sanctions, and they have not ruled out limited military action if Iran or its proxies attack Americans in the region.

However, U.S. military strikes designed to give Iran a “bloody nose” and force the regime to rein in its proxies could lead to a wider, unintended conflagration, with Tehran mobilizing its vast network of proxies and partners from Beirut to Sanaa, Bruce Reidel, a former CIA officer, and other experts said.

Some officials in the administration “have exaggerated expectations of what a bloody nose will lead to,” Reidel said.