Arsène Wenger will add to his Arsenal squad "where it needs" to be strengthened this summer and attempt to sign Samir Nasri and Gaël Clichy to long‑term deals as the club try to secure a first trophy since the 2005 FA Cup.

Defeat at Bolton Wanderers on Sunday left the Gunners nine points behind Manchester United with four games remaining and Wenger admitted their chances of reclaiming the title are now "very unlikely". The Frenchman also said he would not abandon his principles and retains faith in the team's young players, and while he will not top fees for marquee signings, he will be looking to add a few new players – potentially experienced ones – in the summer.

"We have the quality, that is for sure," the Frenchman said. "We have to strengthen the squad where it needs and make the right decision on that front. It [transfers] is always in my mind every day. The team have had an outstanding attitude and will not be rewarded because of small things, but small things cost you. It is frustrating because the team has produced the efforts. We have to be realistic that it [the title] is very unlikely now, but we have to finish as well as we can.

"If someone can convince me that the principles are wrong I am ready to change, but I feel we try to play football the proper way. When you don't win you question your principles, but you have to give yourself the right distance to see what is right and wrong in what you do. I think if something is wrong in our team, it is not the principles in playing our football."

Wenger will look to extend the stays of the France internationals Clichy and Nasri, whose contracts expire next year. Talks have continued with Nasri's representative for some time over a three-year extension, with the midfielder – a £15.8m signing from Marseille in 2008 – having enjoyed a productive season. Yet there is an acceptance that should negotiations remain at deadlock then this summer would represent the best chance for Arsenal to secure an acceptable fee him.

Clichy, the longest-serving member of the senior squad, will open talks at the end of this season, with Wenger optimistic a new contract can be agreed.