ROME, Sept 19 (Reuters) - Christian Manfredini's first goal for Lazio broke the deadlock in a tense first half and the Italian club went on to a comfortable 4-0 win over Greek side Xanthi in their UEFA Cup first round, first leg on Thursday.

Winger Manfredini, who joined the Lazio from Chievo in the close season, made the breakthrough just seconds before halftime before Claudio Lopez, Simone Inzaghi and Cesar added goals in the second period to give the Rome club a comfortable cushion for the second leg in two weeks' time.

The Serie A side had dominated for long stretches of the first half but wasted several good opportunities to score and at one stage it looked like they might suffer the consequences of such profligacy.

They nearly went behind in the 32nd minute when Xanthi's lively midfielder Abderrahim Ouakili launched the ball over the Lazio defence to find Ismaila Ba unmarked on the right.

Ba's volley, however, struck the upright and his follow-up ended harmlessly in the sidenetting.

But once Manfredini's had headed Stefano Fiore's cross between Xanthi's goalkeeper Jurai Bucek and the post, Lazio's attack began to overrun the visitors' static defence.

It all fell apart for Xanthi in 18 frantic minutes of the second half after Argentine striker Lopez had doubled Lazio's lead in the 52nd minute by bursting round Bucek.

Xanthi's defence were again caught leaden-footed in the 67th minute when Inzaghi rose unchallenged to head Dejan Stankovic's cross into the net.

Cesar added a fourth three minutes later after Manfredini had held off three defenders in the Xanthi area.

Lazio coach Roberto Mancini blamed last weekend's 3-2 league defeat at the hands of Manfredini's former club for his team's shaky start.

'It's always difficult to get the first goal,' he said. 'Especially after Sunday's match we were a little bit tense.'