Russia's Gazprom halted natural gas supplies to Poland and Bulgaria on Wednesday as Moscow presses its demand for payment in roubles by countries it deems "unfriendly".
Here are key points regarding how the two countries are equipped to respond:
HOW ARE POLAND AND BULGARIA SUPPLIED?
Gazprom supplies almost half of Poland's annual needs - 10 billion cubic metres (bcm) versus total consumption of over 20 bcm.
Poland covers the rest of its needs with 6.2 bcm via liquefied natural gas (LNG) deliveries shipped to its terminal at Swinoujscie, about 4 bcm in local production and up to 3 bcm piped from the Czech Republic and Germany.
Bulgaria consumes about 3 billion cubic meters of gas per year, and about 90% of that comes from Gazprom imports via Turkey. The country also gets small quantities of gas from Azerbaijan.
HOW MUCH GAS IS IN STORAGE?
Poland's gas storage of 3.5 bcm is 76% full, double its level a year ago, operator data shows, giving it a comfortable cushion to keep supplying customers as requested with the heating season over and consumption usually down to about 1 bcm per month in the warm season.
Bulgaria's gas storage of 550 million cubic meters is only 17.6% full, according to operator data.
WHAT ARE THE ALTERNATIVE SUPPLY OPTIONS?
Poland can source gas via two links with Germany including reverse flows along the Yamal-Europe pipeline while an interconnector with the Czech Republic can supply up to 1.5 bcm annually.
Three further links are due to open this year - a link with Lithuania with an annual capacity of 2.5 bcm on May 1, one with Slovakia with a capacity of 5-6 bcm later in the year, and a 10 bcm pipeline with Norway in October.
Bulgaria will opt to import gas from Greece and Turkey, which can be topped up with imports from LNG terminals in these countries. It will also seek an option to tap common EU gas purchases, its energy minister said.
It plans to complete an interconnector with Greece in June that will allow it to import 1 bcm per year of Azeri gas. At present Bulgaria imports about of third of the quantities provided for under its contract for Azeri gas.
HOW LONG CAN POLAND AND BULGARIA LAST WITHOUT GAZPROM GAS?
Poland's current and pending alternative supply routes suggest Warsaw is safe without Gazprom supply for several months, minister in charge of energy security Piotr Naimski said.
The Bulgarian government said deliveries to consumers have been secured for at least a month ahead and it does not plan to restrict supply for the time being.
Analysts say Sofia should urgently sign deals with LNG suppliers Qatar, Algeria and the United States as well as work to increase Azeri deliveries.
Bulgaria should also seek to sign solidarity agreements with Romania and Greece to ensure it can use any spare gas they have, analysts said.