U.S. Secretary of State Antony Blinken promised a "collective response" to an Iranian drone attack on an Israeli-managed tanker transiting through international waters near Oman last week.
"We are in very close contact in coordination with the United Kingdom, Israel, Romania, and other countries. And there will be there will be a collective response," Blinken said at a regular news briefing.
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The United States was confident that the attack last Friday was carried out by Iran, Blinken said. However, the secretary of state said that the attack was one in a series of actions taken by Iran over many months, and that he was not sure it was "anything new or augurs anything one way or another for the new government."
"But what it does say is that Iran continues to act with tremendous irresponsibility," Blinken added.
Iran denied any involvement in the attack, in which two crew members – a Briton and a Romanian – were killed. After the United States, Britain and Israel blamed Iran for the attack, Iran warned of a "strong" response to any move that threatens Tehran's security.
Earlier Monday, British Prime Minister Boris Johnson said that Iran must face up to the consequences of its "outrageous" attack. "This was clearly an unacceptable and outrageous attack on commercial shipping," Johnson told reporters.
"A U.K. national died. It is absolutely vital that Iran and every other country, respects the freedoms of navigation around the world and the U.K. will continue to insist on that." Britain also summoned Iran's ambassador to the U.K. on Monday.
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The United States and Britain said on Sunday they would work with their partners to respond to last week's attack on the Mercer Street, a Liberian-flagged, Japanese-owned petroleum product tanker managed by Israeli-owned Zodiac Maritime.
Britain said it was highly likely that Iran carried out the attack, using one or two drones.