Spa-Francorchamps witnessed another frustrating afternoon for Fernando Alonso.

Losing position after position as his Honda-powered McLaren lost out to quicker rivals, the Spaniard initially said the situation was "embarrassing". Later in the race, when being given details of his progress, he asked for radio silence, claiming that he would not be doing any further talking, only to break his vow of silence a few laps later with another rant of frustration.

Twenty-five laps into the race, the two-time champion asked if there was any chance of rain, and after being told "no", headed into the pits to retire.

While Honda has claimed that it found nothing wrong with his engine, Alonso has denied claims that his decision to retire was a statement of his dissatisfaction with the Japanese manufacturer.

"It seems that people forget I am racing here, three years, fighting for Q1s, giving my maximum at the start, pushing the car in Hungary in Q1 uphill just to get another run in Q2, and trying to race with a broken rib in Bahrain," he told reporters. "When I read that, I think people are not very concentrated on the real things that happen in Spa. There was much more action in front of me than behind."

Asked why he retired in Belgium, in light of Honda's claim that there was nothing wrong with his engine, he said: "I had a few issues on the power unit, in the three or four laps before the retirement. I've had this a couple of times before where sensors start failing, some things started feeling wrong and it went immediately to engine blow-up.

"This time, after having those first problems, we retired the car and they checked the whole engine. It seems everything is fine on the look they did. We will try to fit that engine tomorrow in FP2. If it blows up we will change it, obviously. If it keeps holding, probably we keep using it."

While the Spa unit will be used in tomorrow's second session, he revealed the latest spec unit will be used in the opening session.

"I think it is 3.7, the name..." said the Spaniard. "When I arrived this morning I asked what was the situation, they said it was still undecided if we will use this race to get the new engine or not this one. Then now, ten minutes ago, they decided to change the engine and get the penalty here."

Check out our Thursday gallery from Monza, here.