Malta, a Mediterranean island country, completed the ratification process for a U.N.-adopted nuclear ban treaty Monday, bringing the number of such countries and regions to 45 with a total of 50 required for the pact to enter into force, a nonprofit antinuclear organization said.

The latest ratification comes on the same day the U.N. General Assembly held a ceremony marking the 75th anniversary of the world body's founding.

With the addition of one more signatory to the Treaty on the Prohibition of Nuclear Weapons, the International Campaign to Abolish Nuclear Weapons, or ICAN, hopes for an early enforcement of the pact, possibly by the end of this year.

Photo taken in September 2018 shows the United Nations flag in New York. (Getty/Kyodo)

However, the treaty's potential effectiveness remains uncertain as all five permanent members of the U.N. Security Council, all of which are nuclear powers, have declined to ratify it.

Japan, the only country in the world to have experienced nuclear bombings, has not ratified the pact either, in light of its security alliance with the United States providing nuclear deterrence against adversaries.

The nuclear ban treaty, adopted in 2017, will enter into force 90 days after it has been ratified by at least 50 countries and regions. According to the United Nations, 84 countries and regions have signed the nuclear ban treaty.

In a related move, a group of 56 former leaders or ministers from countries that depend on U.S. nuclear deterrence on Monday released a letter urging the leaders of their respective countries to participate in the U.N. nuclear ban treaty.

From Japan, former Prime Minister Yukio Hatoyama, former Foreign Minister Makiko Tanaka and former Defense Minister Naoki Tanaka joined the petition.