* Poland wants to stop supplies of Pfizer jabs amid Ukraine war

* EU official says clause invoked by Warsaw was irrelevant

* Warsaw says similar talks with Moderna were very good

BRUSSELS/WARSAW, May 2 (Reuters) - Poland has no "coherent rationale" to invoke force majeure in an existing contract in order to stop paying for more COVID-19 vaccines from Pfizer , a European Commission official told Reuters.

In April Poland's health minister Adam Niedzielski said Warsaw had informed the European Commission and Pfizer that it would no longer take or pay for COVID-19 vaccines under a supply contract co-negotiated by the EU, acknowledging this would trigger a legal conflict.

Poland invoked the force majeaure clause in the contract with Pfizer in the wake of the war in Ukraine which saw an influx of about 3 million Ukrainian refugees into the country.

"There is no coherent rationale to claim force majeure," the European Commission official said, declining to be named because of the sensitivity of the matter.

"The war in Ukraine did nothing to change Poland's vaccination needs, if anything it now needs to vaccinate refugees."

The European Commission declined to comment.

In April a spokesman for the EU executive told journalists that member states were bound by contractual obligations, but Brussels was trying to facilitate a "pragmatic solution".

Pfizer declined to comment on whether it intended to start legal action, but a spokesman said: "Being cognisant of local needs, we are seeking to provide pragmatic solutions to requests whenever possible".

LAW FIRMS INVOLVED

"In the case of Pfizer, we are working with two law firms from Belgium," Wojciech Andrusiewicz, Polish health ministry spokesman, told Reuters on Monday, but said a legal dispute had not formally begun.

"Unfortunately, we cannot see solidarity on the part of the European Commission yet. On the other hand, four other EU countries are interested in negotiations on making contracts more flexible, and they too will start talks soon," Andrusiewicz added, without elaborating.

He said that similar talks with Moderna, which also supplies EU countries with COVID-19 vaccines, were "very good".

Moderna has so far not commented on the matter.

The EU has signed three contracts with Pfizer for the supply of the COVID-19 vaccine it developed with German biotech firm BioNTech. It has also two contracts with Moderna.

Pfizer, by far the main supplier to the EU, agreed last May with EU states the largest supply deal ever signed during the pandemic, guaranteeing up to 1.8 billion vaccines for up to 35 billion euros ($36.8 billion).

EU countries agreed to buy a share of vaccines that was roughly proportionate to their population.

The deal came after the EU had already secured a big volume of vaccines for its population. However, it reckoned more shots were needed after it experienced supply disruptions at the start of the vaccination campaign.

Poland has said the supply under that contract would cost the country over 6 billion zlotys ($1.4 billion) until 2023.

About 60% of the Polish population of 38 million has been inoculated with two doses of COVID-19 vaccines and about one-third has also received a booster shot. This is below the EU average of over 70% fully vaccinated, with half of the population who also got a booster. ($1 = 0.9495 euros) (Reporting by Francesco Guarascio @fraguarascio in Brussels; additional reporting by Pawel Florkiewicz in Warsaw; editing by Emelia Sithole-Matarise)