Tomas Berdych
Berdych kept alive his hopes of reaching the last four with a decisive win over Cilic Getty Images/Julian Finney

Tomas Berdych reignited his ATP World Tour Finals campaign with an emphatic win over US Open champion Marin Cilic in London.

The 2011 semi-finalist roared to a 6-3 6-1 victory in just 74 minutes at the O2 Arena, to put Cilic on the brink of an early exit after just two round robin matches.

Victory for Stanislas Wawrinka over world No.1 Novak Djokovic in the evening session will confirm Cilic's exit on his first appearance at the season-ending tour finals.

Both players knew a second straight defeat would leave them exposed to becoming the first player knocked out of the year-ending ATP finals after heavy losses in their opening matches.

Despite having lost three of the pair's last four meetings, including at the US Open as Cilic went on to claim his maiden grand slam title, Berdych was the marginal favourite to snatch that all important victory.

The two-time Davis Cup winner with the Czech Republic showed his experience on his fifth straight appearance at the O2 Arena to snatch an early break but he was unable to build on his advantage as Cilic clung onto his serve in game six.

Some bold hitting from the Flushing Meadows champion gave Cilic two break points in the next game but errors on the forehand side allowed Berdych to wriggle away to lead 5-3.

The 29-year-old then broke Cilic for a second time as he continued to dictate in the baseline rallies, to take the opening set and with it the match's momentum.

Berdych continued to walk the proverbial tight-rope though and was forced into saving two more break points at the start of the second set, before a skewed Cilic backhand in game four gave him a lead of his own.

And from that moment there was no way back for Cilic as former Wimbledon finalist Berdych continued his crusade towards the last four by taking the second of two match points to win in a little over an hour.