U.S. President Donald Trump said on Wednesday that he will probably meet Russian President Vladimir Putin during his scheduled trip to Europe in July.

"We'll probably be meeting sometime around my trip to Europe," Trump told reporters at the White House during his meeting with visiting Portuguese President Marcelo Rebelo de Sousa.

The location could be in Helsinki or Vienna, he added.

He also said the talks with Putin will focus on Syria and Ukraine.

Kremlin said earlier on Wednesday that the two presidents are expected to meet in a third country, with the date and venue to be announced on Thursday.

The remarks came after Putin's closed-door meeting with visiting U.S. National Security Advisor John Bolton in Moscow.

Bolton's visit reflected "the continued desire of the Trump administration to improve relations with Russia," Dan Mahaffee, senior vice president and director of policy at the Center for the Study of the Presidency and Congress, told Xinhua.

The scholar said Trump, emboldened by his "negotiating successes," felt that he can move forward on meetings with Russia.

However, experts expect the meeting to yield little result, as the Washington-Moscow antagonism is fairly complicated.

Brookings Institution Senior Fellow Michael O'Hanlon said he does not see any specific plan or agenda for the upcoming summit between the two leaders.

Trump is set to attend the NATO Summit in Brussels on July 11-12 and then visit Britain.

He last met Putin in Vietnam on the sidelines of an Asia-Pacific summit in November.

The expected Trump-Putin meeting will be held amid strained bilateral relations due to Russia's alleged meddling in the 2016 U.S. presidential elections, among other thorny issues.

Last August, Trump signed a bill that won a sweeping majority vote in both houses of Congress to impose sanctions on Russia. Afterward, the Trump administration also unleashed a string of sanctions over Russia's allegedly "threatening" activities against the United States.

Earlier this month, Putin signed into law a bill which allows him to respond to sanctions by the United States and other "unfriendly states."