The simpler decision-making should also be used to decide on legislative proposals on Value Added Tax (VAT) and on a common consolidated corporate tax base, which would harmonize national rules on tax deductions, Juncker said.
Juncker is expected to say that the European Union appears to have ridden out the tide of right-wing populism that resulted in the June 2016 Brexit vote and the election of US President Donald Trump last November.
"The amendment is important to make sure that, in the case of a hard Brexit, neither the United Kingdom will have any advantages nor the European Union will suffer from any disadvantages", the EPP said.
In confirming a delay until September 25, which Brussels had been expecting, the British government said in a statement it was a joint decision taken because "more time for consultation would give negotiators the flexibility to make progress".
The head of the EU's powerful executive arm is not expected to dwell on Brexit but will say it is a "huge opportunity" that could end divisions among the remaining 27 members, European sources said.
"Nonetheless, we have to respect the will of the British people". It's not the future of Europe. Britain's official departure in March 2019 and European elections in June 2019 mean the focus will be elsewhere that year.
Juncker, whose Commission proposes European Union legislation and polices the bloc's laws, said the European Union is into its fifth year of economic recovery, with unemployment at a nine-year low.
Mr Juncker told the European Parliament in Strasbourg: "Europe would function better if we were to merge the presidents of the European Commission and the European Council".
Jean-Claude Juncker was speaking two days before European Union finance ministers meet to discuss plans to introduce higher taxes on digital multinationals like Google and Amazon, which stand accused of paying too little tax in Europe.
He paid special tribute to Italy for its "tireless and noble work" at it bears the brunt of rescuing and helping most of the migrants arriving on Europe's shores.
The Financial Times said Juncker would use the speech to push back against Chinese trade, announcing measures to vet foreign takeover bids in sensitive sectors.
Juncker said that he would also propose that the eurozone's bailout fund, the European Stability Mechanism, become a full fledged European Monetary Fund.
"Cyber-attacks are sometimes more risky for the stability of democracies and economies than guns and tanks", he said.