In volatile deals, the pound had dived earlier after Johnson's allies in Northern Ireland's Democratic Unionist Party (DUP) pre-emptively rejected the compromise deal.
Depending on how negotiations go though, they could influence bets of a Brexit delay being followed by a deal.
The pound hit a five-month high against the USA dollar on news of a Brexit deal, then sank back as traders heard Johnson's Northern Irish allies were still unhappy with the way the deal handles the border between Ireland and Northern Ireland - the only land border between the United Kingdom and the bloc and long one of the thorniest issues of any exit.
Sterling, the key gauge of Brexit sentiment, jumped as much as a 1% against the dollar, putting it on course for its best six-day gain in more than 30 years before the doubts and grumbles set in.
This came after US data showed retail sales falling for the first time in seven months in September, suggesting that manufacturing weakness could be spreading to the broader economy, while industrial output for last month also dipped.
Brexit hopes were also providing some support to equity markets in Asia on Wednesday, with Tokyo and Sydney more than one percent higher while Singapore added 0.9 percent.
Of course, if negotiations fall through it could worsen concerns that UK Prime Minister Boris Johnson will attempt to force through a no-deal Brexit at the end of October.
UBS said last week that a "benign deal" could see the pound climb as high as $1.35, while a rejection would likely send the pound lower.
"Where there is a will, there is a deal - we have one!" said European Commission President Jean-Claude Juncker as the news broke from Brussels.
Hopes of a Brexit breakthrough took the pan-European STOXX 600 .STOXX to its highest close since May 2018 on Tuesday, but the index closed down 0.1%.
On Wall Street, Netflix Inc shares rose 2.47% in heavy trade after the video streaming service provider added slightly more paying subscribers than Wall Street expected in the third quarter.
Oil prices were broadly steady on Friday as concern over slower growth in China, the world's biggest oil importer, was countered by bullish signals from both the Chinese and U.S. refining sectors and a North Sea crude disruption that proved temporary.
In the global market, spot gold remained unchanged at $1,491.62 an ounce.
"It looks like a deal is being worked on but everyone who works with the European Union knows that these deals happen at the last minute", said Kit Juckes, head of currency strategy at Societe Generale in London.
Euro zone bond yields were also nudging up with German Bund yields holding at -0.40 per cent, the highest since early August. The Japanese yen JPY= strengthened 0.08% versus the greenback at 108.79 per dollar.
China is expected to post its weakest economic growth in at least 27-1/2 years later in the session, raising pressure on Beijing to roll out more stimulus to counter the effects of the costly trade war.
Benchmark Brent crude oil futures moved between negative and positive territory, trading down 3 cents to $59.88 a barrel by 1328 GMT.
Spot gold was down 0.2% at $1,489.02 an ounce at 1143 GMT.
Rising US-China trade optimism saw demand for safe-haven currencies like United States dollars plummet like a stone.