By Lidia Kelly and Pawel Sobczak

WARSAW (Reuters) - Poland hopes to host U.S. President Donald Trump for a short visit in July and its foreign minister will discuss the plan during a trip to Washington next week, Polish government sources told Reuters.

The diplomatic offensive comes as Poland prepared to welcome on Thursday a U.S.-led deployment of 1,100 troops on its eastern flank as part of NATO plans to counter a more assertive Russia.

Trump rattled Washington's European allies last year by branding NATO "obsolete" and calling for improved ties with Russia. But following a sharp disagreement with Moscow over the Syria crisis, Trump has abruptly reversed course and said on Wednesday NATO was "no longer obsolete".

Trump is due to attend a summit of the Group of 20 biggest economies in Germany on July 7-8. Poland hopes he can make a stopover beforehand in the western Polish city of Wroclaw, which will be hosting a conference on Atlantic values at that time.

"Poland is trying very hard to bring Trump here, even if only for a brief visit," a Polish government source said, on condition of anonymity, late on Wednesday.

A second government source said a Trump visit would be "a significant development for Poland's image abroad".

Poland's conservative, euroskeptic ruling party, Law and Justice (PiS), is staunchly Atlanticist and has been much more welcoming of the new right-wing Trump administration than many other European governments.

Trump has been critical in the past of the European Union, with which PiS has troubled relations.

Polish Foreign Minister Witold Waszczykowski will discuss the invitation in talks next week with U.S. Secretary of State Rex Tillerson, the first government source said.

A source in the office of Polish President Andrzej Duda said Warsaw expected a decision from Washington in the first half of May.

"The case seems to be developing positively, although there is still no final decision," the source said.

NATO Supreme Allied Commander Europe, General Curtis Scaparrotti, was due to attend Thursday's welcoming ceremony for the troops to be deployed in Poland.

(Writing by Lidia Kelly; Editing by Gareth Jones)