ABOARD THE PAPAL PLANE — Pope Francis expressed a potential willingness on Tuesday to mediate a peaceful resolution to the tense political conflict in Venezuela if asked by both President Nicolás Maduro and the opposition leader who is increasingly recognized as the country’s legitimate leader.

“We are always willing,” said Francis on the papal plane returning to Rome from Abu Dhabi, after becoming the first pope to visit the Arabian Peninsula, the birthplace of Islam.

He acknowledged that Mr. Maduro, whose government the United States and many other European countries no longer recognize, had sent him a letter, which he said he has yet to read, asking for a new dialogue.

On Monday, more countries in the European Union recognized the opposition leader, Juan Guaidó, as the legitimate interim president of Venezuela after Mr. Maduro refused to call new elections.