WARSAW (Reuters) - President Donald Trump will attend a summit of the Three Seas Initiative in Poland on Thursday that his hosts hope will boost economic ties between the United States and the ex-communist countries of central and eastern Europe.

Here are some facts about the Three Seas Initiative.

- The Three Seas Initiative is a joint Polish-Croatian project, launched in 2016, with the aim of strengthening trade, infrastructure, energy and political co-operation among countries bordering the Adriatic, the Baltic and the Black Sea.

- The following 12 countries are part of the initiative:

Poland, Hungary, Czech Republic, Slovakia, Romania, Bulgaria, Lithuania, Estonia, Latvia, Croatia, Slovenia and Austria.

- Most of the 12 countries were in the Soviet sphere of influence after World War Two until 1989 and more than half of those joined the European Union in 2004. Nearly all are heavily reliant on Russian gas and oil imports.

- Trump plans to promote U.S. natural gas exports as part of his new “energy dominance” policy while attending the summit.

- Ten of the 12 countries have confirmed attendance at the summit. The presidents of the Czech Republic and Austria will be absent.

- Poland, the EU’s largest eastern economy, has constructed a LNG terminal on its Baltic coast and is eyeing potential exports of the imported gas to other countries in the region.

- The summit’s co-organiser Croatia plans to complete its own LNG terminal in 2019.

- Poland’s ruling right-wing Law and Justice (PiS) party, at odds with the European Commission over a range of issues including rule of law and migrant policy, has put great importance on strengthening co-operation with other countries in central and eastern Europe.

- The PiS government said the construction of the so-called Via Carpatia highway is the most important regional infrastructure project. This will connect Lithuania’s port of Klaipeda with Thessaloniki in Greece, passing through eastern Poland, Slovakia, Hungary, Romania and Bulgaria.

- Currently, there are no north-south highways in eastern Poland and most highways built so far help connect Poland with its biggest trading partner and western neighbour Germany.

- The eurozone is by far the most important trade partner for most countries in central and eastern Europe, with inter-regional trade accounting for a much smaller share.

- In the case of Poland, exports to the eurozone accounted in 2016 for 57 percent of total exports, while exports to non-eurozone EU members such as Hungary, the Czech Republic, Romania and Bulgaria for 23 percent