Bahrain has become the second Arab country in a month, after the UAE, to normalize ties with Israel under U.S. mediation after decades of animosity.
The rapprochement has been welcomed by some Arab countries, but others have rejected the U.S. initiative and many view it with caution.
During a Middle East tour in late August which took in Israel, Sudan, Bahrain and the United Arab Emirates, Secretary of State Mike Pompeo expressed optimism that more Arab nations would sign up.
Analysts had seen Manama and Khartoum as most likely to follow in the footsteps of the UAE, which on August 13 became only the third Arab nation to have diplomatic ties with the Jewish state.
Regional heavyweight Saudi Arabia, while not condemning the deal, has refused to normalize ties until Israel signs an internationally recognised peace accord with the Palestinians.
But it has allowed virtual client state Bahrain, on the 9/11 anniversary, to follow in the footsteps of Riyadh's ally Abu Dhabi.
Oman
Oman also welcomed neighbour UAE's deal with Israel but said it stayed committed to "the legitimate rights of the Palestinian people who aspire to an independent state" with east Jerusalem as its capital.
The country is also a close U.S. ally but at the same time has good relations with Iran. It maintains a policy of neutrality and has over the years played a mediating role in regional conflicts.
There have been several contacts between Oman and Israel, including in 2018 when the late Sultan Qaboos received Prime Minister Benjamin Netanyahu in Muscat.
Sultan Haitham, who was sworn in in January after the death of Qaboos, is "already treading lightly due to possible economic-related grievances and would not risk such a controversial move at this time", according to Cinzia Bianco, a research fellow at the European Council on Foreign Relations.
Qatar
Qatar has not responded to the surprise UAE announcement amid a protracted diplomatic standoff with Abu Dhabi, Riyadh, Manama and Manama - which accuse it of supporting Islamist movements and conniving with Iran, charges it denies.
Doha, which is also close to the US, has an on-again, off-again relationship with Israel, after hosting an Israeli economic interests office from 1996 until 2000.
It is heavily engaged in the Gaza Strip, managing and funding welfare payments to the Palestinian people of the impoverished coastal territory with Israel's blessing.
"While Qatar cooperates with Israel in support of the Palestinian cause... it will not normalise relations as long as the peace process is stalled," Krieg said.
Kuwait
Kuwait has likewise opted to stay silent.
The wealthy emirate is the only country in the Gulf with a genuine political and parliamentary life, and at times permits lively public debate.
Some political groups and civil society organizations have condemned the UAE's decision, while others have defended it.
But formalization of ties with Israel is unlikely, as the National Assembly has capitalised "on hostility towards Israel to claim its place as the voice of the people", Bianco said.
Sudan
Several factors could encourage Sudan to move towards normalization, but it told Pompeo during his visit that Khartoum could not establish diplomatic relations for now, dashing hopes for a speedy breakthrough.
Sudan, grappling with an acute economic crisis, seeks to be removed from a U.S. blacklist as an alleged state sponsor of terrorism.
And General Abdel Fattah al-Burhan, who heads Sudan's transitional sovereign council, met with Netanyahu in Uganda in February.
After the UAE's announcement, officials initially issued contradictory comments.
Foreign ministry spokesman Haider Badawi voiced backing for such an accord, but Foreign Minister Omar Gamaledinne said it "has never been discussed by the Sudanese government" and promptly fired him.
Late last month, Prime Minister Abdalla Hamdok told Pompeo that Sudan's transitional government - which replaced ousted strongman Omar al-Bashir last year and is set to rule until 2022 polls - has "no mandate" to take such a weighty step.
But Bahrain, during Pompeo's charm offensive across the region, had initially also distanced itself from a swift normalization with the Jewish state.
Sudan, unlike Gulf states, has for decades been technically at war with U.S. ally Israel. Under Bashir, the central African country for years supported hardline Islamist forces.