Analysts say sterling's fall will deepen if Mr Johnson launches a leadership challenge to Theresa May.
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US Dollar (USD)
USD/EUR - Today's data summary
% change
-0.16%
Price Euros
0.8575
Change
-0.0010
As of 18:16 19 Jul 2018
USD/GBP - Today's data summary
% change
+0.26%
Price Pound sterling
0.7670
Change
+0.0020
As of 18:16 19 Jul 2018
USD/JPY - Today's data summary
% change
-0.44%
Price Yen
112.3500
Change
-0.5000
As of 18:16 19 Jul 2018
Latest updates
Dollar slips against yen
The dollar has fallen to a two-week low against the yen on the back of the latest global trade war concerns.
The Wall Street Journal reported that the US Treasury Department is putting together rules that would block firms with at least 25% Chinese ownership from buying US companies involved in “industrially significant technology”.
Markets react to US jobs numbers
The US share markets will open in about half an hour. Signs are they will open about 1% lower. Jobs growth was on the disappointing side - markets expected almost double the 103,000 new jobs - and wage growth was a bit faster than expected.
The dollar fell a tiny bit against the yen in the wake of the jobs announcement. It is now down 0.07% against the Japanese currency at 107.35 yen.
Meanwhile the pound is up a little against the dollar at 1.4017.