The new president did not announce any shakeup in the defense or foreign ministries, where changes could be pivotal for Ukraine's ongoing offensive in the east. Ukrainian officials say at least 200 people, including 59 servicemen, have been killed in clashes in the east.
It is unclear how many civilians in the east have fled the fighting. The United Nations' refugee agency in May said Ukraine's tensions had resulted in about 10,000 displaced people, both from Russia's annexation of Crimea and from the violence in the east.
Russian Foreign Minister Sergey Lavrov on Tuesday said some 30,000 Ukrainian refugees are now in Russia's Rostov region, which borders Ukraine.
Lavrov, after meeting with his German and Polish counterparts in St. Petersburg, said the announcement on establishing safe passage was "a step in the right direction," but criticized Ukraine for continuing the offensive.
"The key to toning down the situation in our view is ending this military operation against protesters. Then, I am convinced, these people who you call separatists will take reciprocal action," he said.
The government in Kiev calls the security sweep an "anti-terrorist operation." Russian officials deny allegations by Kiev and Western countries that it is fomenting or supporting the uprising in the east and it is uncertain how much influence Moscow can exert on the insurgents.
Poroshenko's statement gave no indication that he was planning to wind down the government's operation against the rebels, who have continued to seize administrative buildings, police stations, border posts and garrisons across the region.
At his inauguration on Saturday, Poroshenko said he would grant amnesty to any insurgents who laid down their arms and had not been involved in bloodshed, and encouraged the creation of a safe corridor for rebels to go to Russia. He ruled out negotiations with any "gangsters and killers" among them.
U.S. Assistant Secretary of State Victoria Nuland, who spoke to journalists briefly in Kiev on Tuesday, praised Poroshenko's plan to resolve the conflict and promised that $48 million pledged by Vice President Joe Biden to Kiev on Sunday would be used "in eastern Ukraine in conjunction with the president's peace plan."
Jim Heintz in Moscow contributed to this report.