WASHINGTON - The United States vowed to assert a "snapback" of all prior international sanctions on Iran, effective 8 p.m. Eastern Time on September 19, with more announcements to be made this weekend and next week as to exactly how Washington is planning to enforce the "returned U.N. sanctions."

"We will return to the United Nations to reimpose sanctions so that the arms embargo will become permanent next week," said U.S. Secretary of State Mike Pompeo Wednesday during a joint press conference with British Foreign Secretary Dominic Raab.

"I think we absolutely agree that Iran must never be - never be allowed to obtain a nuclear weapon," said Raab. "We also, I think, share the view that the diplomatic door is open to Iran to negotiate a peaceful way forward. That decision, that choice is there for the leadership in Tehran to take." He stopped short of saying whether or not and how Britain will implement the snapback sanctions.

Britain, France and Germany, the so-called E3, said in August that they cannot support the U.S. move to restore U.N. sanctions on Iran, saying the action is incompatible with efforts to support the Iran nuclear deal.

"Whether those countries will in fact ignore the U.N. sanctions [under U.N. Security Council resolution 2231] remains to be seen," U.S. special envoy for Iran and Venezuela Elliott Abrams told reporters in a Wednesday phone briefing. He added the E3 and other European countries had told Washington that they don't want the Iran arms embargo to end, but they were unable to take any action that kept the UN arms embargo in place.

Abrams said the returned sanctions include "a ban on Iran engaging in enrichment and reprocessing-related activities, the prohibition on ballistic missile testing and development, and sanctions on the transfer of nuclear and missile-related technologies to Iran."

U.S. officials warn that an Iran free from restrictions would lead to further regional destabilization, intensified conflicts and a regional arms race.

The U.S. tried but failed on August 14 to extend an expiring arms embargo against Iran through a resolution at the United Nations Security Council.

The embargo against the sale or transfer to or from Iran of conventional weapons is set to expire on October 18, under the 2015 nuclear deal, known formally as the Joint Comprehensive Plan of Action (JCPOA).

With the extension blocked, Washington saw triggering a snapback of U.N. sanctions under Security Council Resolution 2231, which implemented the Iran nuclear agreement, as the only path for restoring the arms embargo.

As the U.S. prepares to snap back sanctions against Iran this weekend, E3 nations are largely seen as likely to ignore them. Some experts said there would be a limited impact on European economies, unless the U.S. punishes those nations with secondary sanctions.

"The immediate U.S. goal in trying to re-impose sanctions is to prevent the end of the U.N. arms embargo in mid-October. But even if the Europeans recognize the U.N. embargo ends next month, British and EU companies are not going to start selling tanks to Tehran. The U.S. expects Chinese and firms to look for arms deals, and they will probably sanction those companies bilaterally. But that doesn't bother the Europeans very much," said Richard Gowan, U.N. director of International Crisis Group (ICG).

"Overall, the U.S. has realized that this is not a useful fight to pursue," Gowan told VOA on Wednesday. "Equally, E3 diplomats say that they would prefer to avoid a big public row over snapback too, to limit the harm to relations with Washington."

Under the JCPOA concluded on July 14, 2015, the five permanent U.N. Security Council members, plus Germany, agreed with Iran to gradually lift international sanctions in return for limits on Tehran's nuclear activities, to prevent it from making a nuclear bomb. It also opened Iran's markets back up to many foreign investors.

The United States withdrew from the deal in May 2018, re-imposing unilateral sanctions on Iran. In response, Tehran resumed some of its nuclear activities, and in July 2019, it breached the deal by exceeding limits on both uranium enrichment and stockpile levels. Iran denies that its nuclear activities are for military purposes.