Islamabad (Agencies): Efforts of John Kerry, chairman of US Senate's Foreign Relations Committee, seem to have gone in vain as Pakistan's civil and military establishments are in a defiant mood on the issue of granting diplomatic immunity to Raymond Davis.

Davis was detained by Lahore police on January 27 on charges of killing two alleged robbers. He has claimed that he acted in self-defence and the case is proceeding in a local court.

After high-level contacts to secure his release on diplomatic grounds were not entertained by the Pakistani government, Kerry reached Pakistan on Tuesday on a diplomatic mission for the release of the US official.

Kerry called on President Asif Ali Zardari, Prime Minister Yousuf Raza Gilani, opposition leader Nawaz Sharif and Pakistan Army chief General Ashfaq Pervez Kayani on Wednesday to advocate for the discharge of Davis "to protect deep-rooted bilateral relations between both countries".

"The matter is not as simple as it looks. The case is now in court, which is going to decide it on merit," Zardari replied Kerry.

Gilani admitted that the "government is facing difficult times on the issue". "We have not bowed to any pressure and would respect the decision of the courts," he stated.

Nawaz Sharif, whose party PML-N is in regime in Punjab province where Davis is under trial, was more staunch and blunt in his stance after the meeting with Kerry.

"We have had constructive discussions and I am hopeful that the matter will be resolved within 3-4 days," said Kerry at Chaklala air base in Rawalpindi before flying back to the US after the meetings.