The 82-year-old was speaking at the 29th annual Arab League summit in the oil-rich Saudi city of Dhahran.
HM the King delivered a speech in which he extended thanks and appreciation to the Custodian of the Two Holy Mosques King Salman bin Abdulaziz Al-Saud for inviting him to take part in the Arab Summit.
Leaders of several Arab countries will attend the summit and they will hold closed-door talks to discuss the summit agenda.
In his speech at the summit, King Salman stressed that the Palestinian issue is "our first issue and will remain so" expressing his condemnation of the decision of the USA administration to transfer its embassy to Jerusalem.
HM the King also expressed thanks and appreciation to HM King Abdulla II of Jordan for his wise leadership of the Arab Summit during his presidency, citing Jordan's initiatives and clear contributions to enhancing joint action.
AL Secretary General Ahmed Aboul-Gheit noted that the crises gripping the Middle East will further deteriorate and weaken the entire region if not harnessed.
Saudi Foreign Minister Adel al-Jubeir said on Thursday that Qatar's crisis would not be on the table at the Arab League summit, Al Arabiya reported.
"The Saudis are going to push for a much harsher stance on Iran - not necessarily on the nuclear dossier per se, but on Iranian influence in the Arab countries, particularly Iraq, Syria, Lebanon and Yemen", said Karim Bitar of the Paris-based Institute of worldwide and Strategic Affairs.
The first of these leaders to arrive in Saudi Arabia were Somali President Mohammed Abdullahi Farmaajo, Egyptian President Abdul Fattah al-Sisi, Iraqi President Fouad Maasum, Comoros President Azali Assoumani, Tunisian President Beji Caid Essebsi, Lebanese President Michel Aoun, Palestinian President Mahmoud Abbas, Yemeni President Abdrabbuh Mansur Hadi, United Arab Emirates Vice President Sheikh Mohammed bin Rashed al-Maktoum, Libyan Prime Minister of the Government of National Accord Fayez al-Sarraj and Omani Deputy Prime Minister for Cabinet Affairs Fahd bin Mahmoud al-Saeed.
"We reiterate our rejection of the United States decision on Jerusalem", the king said in a speech in Dhahran in eastern Saudi Arabia.
"We renew our optimism of the leadership of the Custodian of the Two Holy Mosques and his great efforts to ensure a strong Arab role, a unified position and a clear message that the worldwide community understands, appreciates and responds to", HM the King added.