David Cameron and Nick Clegg will stage a show of coalition unity on Monday as they launch plans for the biggest investment programme in the railways since the Victorian era.
The Prime Minister and Deputy Prime Minister will highlight a £9 billion injection into the network as they seek to draw a line under the latest bout of sniping between their two parties.
Their appearance together coincides with a Cabinet "awayday", with senior ministers leaving London for their final meeting before MPs break for the summer recess.
He said it was essential that differences over Lords reform did not stop them working together in government in the national interest. However his appeal failed to halt the angry exchanges in the wake of last week's Tory revolt which threatens to derail the plans.
Former Lib Dem leader Sir Menzies Campbell warned his party's MPs may refuse to back Conservative plans to redraw parliamentary boundaries - thought to be worth an extra 20 seats to the Tories at the next general election - unless Lords reform goes ahead.
On the Conservative side, the chairman of the Tory backbench 1922 Committee, Graham Brady, said he believed the coalition was now "very likely" to come to an end before the general election, set for 2015.
"I think it would be logical and sensible for both parties to be able to present their separate vision to the public in time for the public to form a clear view before the election," he told BBC Radio 4's The Westminster Hour.
"Of course, it is always possible that that moment of separation could come sooner. It's very difficult to predict when that might be."
Mr Cameron frankly acknowledged there were "profound areas of disagreement" between the two parties but said it was essential that they continued to work together in Government in the national interest.
Monday's announcement on rail investment covers the period 2014 to 2019 and is expected to include £5 billion for the completion of ongoing projects such as Thameslink and the cross-London Crossrail and £4.2 billion for new schemes.
Among the projects expected to benefit are:
:: Electrification - completion of the Midland Main Line from Bedford to Sheffield, local lines in the Welsh Valleys, and an extension of the already-announced electrification between Manchester and Leeds;
:: The Northern Hub: A series of projects around Manchester that improve northern rail capacity so as to get more and faster trains across the north of England;
:: Upgrades to the East Coast Line from London to Leeds and Newcastle;
:: The reopening of the east-west link from Oxford and Aylesbury to Milton Keynes in Buckinghamshire;
:: Electrification of the lines from London to Bristol and Cardiff, and from Manchester to Liverpool, Blackpool and Leeds.
Shadow transport secretary Maria Eagle said the investment programme must not be paid for by further fare rises for hard-pressed rail users.
"Government promises of rail investment after 2014 do not justify inflation-busting fare rises now. None of the rail schemes being pledged this week will see a penny of money spent on them until at least 2014 with many of the improvements not benefiting passengers until the next decade," she said .
"Passengers facing another two years of fare rises of up to 11% will be unimpressed by ministers trying to suggest that there is any link between fare rises now and promises of investment beyond the next election."
Bob Crow, general secretary of transport union the RMT, said: "What we need is investment in rail today not yet another political promise of jam tomorrow.
"All of the rail projects on this shopping list have been talked about for years and with the surge in passenger demand we cannot afford further delays like the ongoing Thameslink fleet replacement fiasco. We have the chance to create thousands of rail jobs if the politicians wake up and get these projects moving."