Jordan has condemned a decision by Israel to advance a plan to build a railway line and station underneath the heart of Jerusalem's Old City.
The Israeli transport ministry said on Monday that a new route had been approved for an extension of the Tel Aviv-Jerusalem high-speed railway.
A 3km (2-mile) tunnel will lead to the Western Wall - one of Judaism's holiest sites - in the city's occupied east.
Jordan called the move a "flagrant violation of international law".
Foreign ministry spokesman Daifallah al-Fayez urged the international community to "assume its responsibilities to resist the illegitimate and illegal Israeli steps".
Jordan has special responsibility for overseeing the Muslim holy sites in Jerusalem - including the compound behind the Western Wall, known to Muslims as al-Haram al-Sharif (the Noble Sanctuary) and to Jews as the Temple Mount - via an Islamic trust called the Waqf.
The status of Jerusalem goes to the heart of the Israeli-Palestinian conflict.
Israel regards Jerusalem as its "eternal and undivided" capital, while the Palestinians claim East Jerusalem - occupied by Israel in the 1967 Middle East war - as the capital of a future state.
The Israeli plan to extend the Tel Aviv-Jerusalem high-speed line to the Western Wall, which attracts millions of visitors and worshippers a year, was unveiled in 2017 by then Transport Minister Israel Katz.
He also said the station underneath the Old City would be named after US President Donald Trump, who controversially recognised Jerusalem as Israel's capital that year.
On Monday, the Israeli transport ministry announced that the National Planning and Building Council had approved a new route for the railway extension following a directive from Mr Katz's successor, Bezalel Smotrich, according to Israeli media.
It did not provide any details about the route, but it will reportedly involve building two underground stations and digging a tunnel beneath central Jerusalem.
Mr Smotrich described the plan as "historic" and said it was "very good news for Israeli residents and the millions of tourists who come to Jerusalem".
"We are also succeeding in promoting the Zionist and Jewish agenda," he added.
Last November, the Israeli authorities approved a plan to build a cable-car network that would ferry visitors 1.4km from West Jerusalem to the Western Wall.
Officials said the project would reduce traffic congestion, but critics said it would damage the historic landscape of the Old City - a Unesco World Heritage site.