West Ham United's squad strengthening ahead of a second campaign in the Premier League is to begin with the free transfer arrival of the experienced Romania defender Razvan Rat when his contract at Shakhtar Donetsk expires in June.

The left-back, who captains his national side and has 88 caps, is to sign a three-year contract at Upton Park worth around £35,000 a week as Sam Allardyce, who intends to sign a new deal at the club himself, seeks to upgrade the playing staff in order to establish West Ham firmly in the top flight.

Rat has spent the past decade at the Ukrainian club and won six league titles with Shakhtar, while also featuring heavily in Uefa competition in that time. The 31-year-old had been subject of interest from Marseille in January but, although the French club had hoped to compete for his signature in the summer, their bid has been eclipsed by West Ham's wage offer, with the deal expected to be announced before the end of the season.

Left-back has been a problem position for the London club this term. Allardyce brought George McCartney back to Upton Park last summer only for the defender's impact to be frustrated by injury, leaving Joey O'Brien standing in for much of the campaign. Although he has performed capably, there is a recognition that further strengthening was required even after a successful season back among the elite.

"To improve we just need to add better players, it's a simple as that," Allardyce said last week. "If we get better players, then we improve. If we can do that, then we get better and we become an established Premier League side."