Two players who may have slipped off England's radar kept Warwickshire out of trouble in their LV County Championship meeting with Division One strugglers Worcestershire at New Road.

Tim Ambrose, who played his last Test in the West Indies in February, and Rikki Clarke, the former Surrey all-rounder who bowed out of the international arena in 2006, romped to a century partnership as Warwickshire made 309.

The home side only had time to make two without loss before rain ended the first day in meeting of two counties without a win this season.

Warwickshire were rocking at 160 for five when Jonathan Trott went for 67, but Ambrose and Clarke launched a counter-attack to take full advantage of a let-off for Ambrose before he had scored.

After reviving their side by putting on 116 in 23 overs, the sixth pair were swept up by Matt Mason and Richard Jones in a spirited response by Worcestershire's injury-hit attack after tea.

Mason, shouldering the main workload with two for 51 from 21 overs, had Ambrose caught at second slip for 63 and Jones, with a career-best four for 66 in his fourth Championship match, bowled Clarke for 50.

Unlike last week, when Worcestershire conceded a total of 428 for six after putting Somerset in to bat, Vikram Solanki received a better reward when he again elected to bowl first on a green-looking pitch.

Warwickshire's decision to use Neil Carter as an opener - his regular role in one-day cricket - met with limited success as the left hander hit three fours before playing to the recalled paceman, Imran Arif.

A fallible top order quickly met with further problems. Ian Westwood (22) drove Gareth Andrew's sixth delivery to Solanki at cover and Jim Troughton, after facing 32 balls for six runs, edged Jones for the first of Daryl Mitchell's three catches at second slip.

The in-form Trott initiated a recovery with Tony Frost (37) in a stand of 75 but both were caught behind as Mason and Jones pegged back the scoring following a flurry of boundaries immediately after lunch.

The day then took a decisive twist when Ambrose survived a low chance to Alexei Kervezee after clipping Mason to square leg. This enabled the Australian-born wicketkeeper to re-discover his form after an erratic season with the bat.

Having started with 327 runs from three knocks - including centuries for Warwickshire and England Lions - he added only 90 in his next nine first-class first-innings and failed to make England's provisional squad for the Champions Trophy at the end of the season.

His undoubted quality resurfaced with 13 fours as Worcestershire lost control in an afternoon session of 158 runs from 34 rovers, but it was a different story when Warwickshire struggled to secure a third batting point.

After losing Ant Botha and Chris Woakes in successive overs from Gareth Andrew (three for 57), they edged past 300 before Jones completed his best day in county cricket by bowling Boyd Rankin.