Billy Hayes insisted the CWU's power was "exercised quite sparingly"
The postal workers' union's head has said he is prepared to stage further industrial action before Christmas.
The Communication Workers Union has announced two nationwide strikes next week due to an escalating row over pay, working conditions and reform.
General secretary Billy Hayes told the Times that he was "not ruling anything out", including more stoppages.
Mr Hayes also suggested that he was in a stronger position than former miners' leader Arthur Scargill in the 1980s.
The 24-hour strikes will begin on 22 October. On the first day, mail centre staff and drivers will strike. The next day it will be delivery and collection staff.
Mr Hayes told the newspaper that although the CWU was trying to reach agreement with Royal Mail, its planned 48-hour walkout - due begin this Thursday - may not be the last.
Asked whether his position was stronger than that of Mr Scargill before the 1984-5 miners' strike, Mr Hayes replied: "Yes. I think in terms of the impact of the Royal Mail on the economy, it's stronger. There's no doubt."
EXPECTED STRIKE DISRUPTION
22 October: Limited processing, movement and collection of mail
23 October: Limited delivery and collection of mail
Some managerial staff and contract drivers will be brought in to move mail but services will be "very limited"
Special Delivery and Royal Mail Tracked items will still be delivered on strike days
Post Office branches will be open as usual although collections will be affected
Parcelforce will operate as normal as it has its own collection, distribution and delivery network
Customers should check the Royal Mail website or call 08457 740 740 for the latest service information
Source: Royal Mail
Mr Hayes said the miners' leader Mr Scargill had failed to secure authorisation for the 1980s strikes via a ballot and had been confronted by a government which had stockpiled coal.
By contrast, he said, the CWU had secured a majority vote in favour of industrial action.
"Mail volumes increase by three times in the run-up to Christmas and the thing about mail is that it's not something you can stockpile," Mr Hayes added.
"What this means is that the impact of any future action will not be unimportant. Royal Mail is a key sector of the economy."
However, he offered Royal Mail management the opportunity of arbitration through Acas and said it would "be foolish of me not to be mindful of the impact of a strike" on the economy.
He said: "We don't apologise for having influence and power. But that power is exercised quite sparingly."
Previously, a document leaked to BBC's Newsnight programme appeared to show Royal Mail digging in for a bitter battle against the union.
Dated 24 September 2009 and marked "In strictest confidence", the document says that "through the dispute" the Royal Mail will "deliver the necessary 2009 changes with or without union engagement".
Royal Mail said it '"did not recognise" the document and said it did "not reflect Royal Mail's policy, strategy or position in relation to the current dispute with the CWU".