As a looming deadline approaches for the Iran nuclear deal, there may be a plan to prevent the United States from pulling out of the agreement -- essentially a workaround that would help President Trump deliver on a campaign promise of renegotiating the deal.

"Face the Nation" moderator Margaret Brennan reports the U.S. and its European allies would create a proposal that addresses Mr. Trump's concerns about the agreement -- ballistic missiles, military site inspections and the sunset clause -- thus allowing Mr. Trump to claim he "fixed" the 2015 international agreement without actually altering a word of the agreement and without Iran's consent. It would be a workaround to help the U.S. and its allies promise to punish Iran for actions that were not included in the 2015 deal. This plan wouldn't include Russia, China and Iran.

The U.K. ambassador to the U.S., Sir Kim Darroch, told "Face the Nation" Sunday that Mr. Trump told British Prime Minister Theresa May there was no decision yet regarding the May 12 deadline. Although the U.S. and its European allies had not yet agreed on a separate deal for Mr. Trump to sign off on, Darroch thinks a decision could be reached as early as the end of the week.

Meanwhile, the U.K.'s top diplomat, Boris Johnson, arrived in Washington on Sunday afternoon to lobby the White House to stick with the original Iran deal. Johnson wrote an op-ed published Sunday in The New York Times, serving as a reminder as to how the Iran nuclear agreement "helped avoid a possible catastrophe." Johnson said the agreement is imperfect, but could be mitigated.

British Foreign Secretary Boris Johnson seen Nov. 4, 2016. Getty

"It has weaknesses, certainly, but I am convinced they can be remedied," Johnson wrote. "Indeed at this moment Britain is working alongside the Trump administration and our French and German allies to ensure that they are."

"Imagine all the mutually contaminating civil wars and internecine conflicts that rage across the Middle East today," Johnson added. "Then turn the dial and add the possibility of a regional nuclear arms race triggered by Iran dashing for a bomb. That is the scenario which the agreement has helped to prevent."

He pointed out that "it would be a mistake to walk away from the nuclear agreement and remove the restraints that it places on Iran."

Mr. Netanyahu has called on Mr. Trump to scuttle the deal, recently describing how Iran conducted a secret project between 1999 and 2003 to research the technology for a nuclear weapon. But that project actually underscores the importance of maintaining the restrictions on Tehran's nuclear ambitions, including the IAEA's ability to inspect key facilities."

While in D.C., Johnson will meet for two days with Vice President Mike Pence and other senior Trump administration officials, including National Security Adviser John Bolton. He also will discuss key issues with congressional foreign policy leaders about Iran, North Korea, Syria and other international issues.

"On so many of the world's foreign policy challenges the U.K. and U.S. are in lockstep," Johnson said in a statement before his travel to Washington. "We've seen this recently with the response to the poisonings in Salisbury, our strong response to Assad's use of chemical weapons in Syria, and the effort to denuclearize North Korea."

Not to be forgotten, Iran's president has warned that the U.S. would face "grave" consequences if they decided to formally pull out of the Obama-era nuclear pact. Darroch said the plan for now is keeping the U.S. a part of the deal.

"Of course we are looking at all eventualities. My government has said that as long as Iran is in compliance with the deal and wants to stick with it that will be our position as well, so we're looking at options for maintaining the deal should -- which we hope they won't -- should the U.S. administration choose to withdraw."

The May 12 deadline is one imposed by Congress that requires the president to confirm whether or not Iran is in technical compliance thus determining whether sanctions should continue to be suspended. The State Department, Department of Defense, and CIA all say Iran is in compliance and so do the United Nations inspectors at the International Atomic Energy Agency (IAEA).

If Mr. Trump allows sanctions to be put back on without cause, then that could put the U.S. in violation of the deal and effectively pulls the country out of it, Brennan reports.