ISTANBUL/BERLIN (Reuters) - A delegation of German lawmakers visited Incirlik air base in southern Turkey on Wednesday, defusing a months-long row that had prevented them meeting troops serving in the coalition against Islamic State.

Karl Lamers, a member of Chancellor Angela Merkel's conservative Christian Democrats, said the visit had paved the way for parliament to vote to extend the deployment of nearly 240 German troops stationed at the base.

"The Bundestag has got access to the troops and that means nothing stands in the way of an extension of the German military mission in December," Lamers told the RND newspaper group.

Lawmakers had threatened to end the deployment when its mandate expires in December.

The German Air Force has kept Tornado surveillance jets and a refueling plane at Incirlik to contribute to the fight against Islamic State. The German soldiers are at Incirlik to help defend Turkish troops against possible attacks from Syria.

Turkey in June barred the politicians from the base in response to a resolution in the German parliament declaring the 1915 massacre of Armenians by Ottoman forces a genocide.

In July, Turkey briefly grounded coalition planes at Incirlik after an abortive military coup and amid concerns that rogue troops might try to flee the country from the base.

The U.S. Air Force has around 5,000 personnel at Incirlik, which serves as a hub for the U.S.-led coalition trying to defeat Islamic State over the borders in Syria and Iraq.

Merkel in September persuaded President Tayyip Erdogan to allow the parliamentarians to visit. Their trip is taking place with little publicity. Anadolu said it was closed to media.

Lamers said German lawmakers had an "open, honest" dialogue with Turkish officers and there were no restrictions on their ability to move around the base.

Another German lawmaker, Agnieszka Brugger, a member of the Green party, told RND housing facilities for the German troops at the base were not satisfactory. Germany plans to invest 58 million euros to improve infrastructure at the base, including new quarters for troops.

NATO allies Germany and Turkey have crossed swords in recent months over the flow of migrants to Europe through Turkey and German criticism of the Turkish response to the coup attempt, which has included a purge of security and civil service personnel and the arrests of more than 30,000 people.

German prosecutors said on Tuesday they had dropped an investigation of a comedian accused of offending a foreign leader after reciting an obscene poem about Erdogan on national television. Erdogan had filed a complaint against the comedian, Jan Boehmermann.

Boehmermann released a video on Twitter on Wednesday in which he welcomed the decision and called the situation "a big sad joke given what journalists, satirists and opposition figures have had to and continue to endure in Turkey."

(Writing by Ayla Jean Yackley and Daren Butler and Andrea Shalal in Berlin; Editing by Janet Lawrence)