The president summoned thousands of troops to Ukraine's capital Saturday, but forces loyal to the nation's prime minister stopped them outside Kiev, escalating the two leaders' ongoing power struggle.

Soon after, the feuding leaders agreed to hold an early parliamentary election on Sept. 30, diffusing the country's months-long political crisis that had threatened to escalate into violence.

Tensions have grown since President Viktor Yushchenko ordered parliament disbanded in April, claiming Prime Minister Viktor Yanukovych and his supporters were trying to usurp presidential power. This week, the president moved to fire the nation's chief prosecutor and take control of Interior Ministry troops, adding to the acrimony.

The ministry's 32,000 troops answer to the interior minister, a Yanukovych loyalist. But Ivan Plyushch, the head of the national security council, said the president had ordered the troops to Kiev to forestall violence, though some feared it would have the opposite effect.

"Moving the interior troops into the city is necessary to guarantee a calm life for the city, to prevent provocations," Plyushch was quoted on the presidential Web site.

The statement did not specify how many troops have been sent, but Nikolai Mishakin, deputy commander of the interior troops, said on Ukrainian television that nearly 3,500 officers had been prevented from entering Kiev by forces loyal to Yanukovych. Mishakin promised his troops would not resort to violence since none of them had firearms.

AP Television News showed footage of several convoys of troops stopped on their way to Kiev from central and western provinces. Dozens of officers got out of the buses and waited patiently in a forest by a highway — some laying on grass, others drinking water, smoking, chatting and appearing relaxed.

Yuri Ivakin, a senior official in the Kiev city administration loyal to Yanukovych, stopped two buses outside the capital. He told the AP that he would try to turn troops back to their bases. Ukrainian television later reported that the officers left the buses and marched toward Kiev.

The Western-leaning Yushchenko came to office in 2005 after the Orange Revolution protests and surviving poisoning that marred his face. His agenda, however, has been complicated by fighting among his supporters and the ongoing disputes with Russia-leaning Yanukovych.

As parties loyal to both sides warned Saturday of possible violence, Yanukovych and Yushchenko met again to try to defuse the crisis. Earlier meetings ended without visible progress.

Several hundred flag-waving supporters of both leaders held competing rallies in front of the presidential office, where Yushchenko and Yanukovych were meeting. A thin line of police separated the two camps of protesters.

Yushchenko dissolved parliament on April 2, but Yanukovych's supporters in parliament have defied the order, calling it unconstitutional.

Both leaders have agreed to respect the Constitutional Court's decision on the dissolution order, but the court has been deliberating on the matter for weeks. The hearings were complicated by Yushchenko's orders to fire several of its judges, including the chief judge.

Then, on Thursday, Yushchenko fired longtime foe Prosecutor General Svyatoslav Piskun — a Yanukovych ally — saying Piskun could not serve as the country's chief prosecutor while acting as a member of parliament.

Security officers were sent to oust Piskun, but riot police loyal to Yanukovych immediately moved to protect him, standing guard outside his office.

Piskun appealed to a Kiev district court and late Friday said the court ruled to reinstate him. The ruling could not be immediately confirmed, and a Yushchenko aide said Saturday that Piskun was lying.

Tensions further grew when Yushchenko claimed command of Interior Ministry troops — an order rejected by the ministry headed by Vasyl Tsushko, a Yanukovych loyalist.

Yanukovych's allies called for calm and restraint, but warned they would not back down in the dispute. Tsushko promised not to use force, but his deputy, Korniyenko, said the ministry would fend off any attempts to take it forcefully. "Let them try, we have what we need to respond," Korniyenko said.

Piskun lamented that "cannon fodder was being sent to Kiev," adding that he would not hesitate to fire officials who violate the law.

"As long as I'm prosecutor-general in this country, there will be no scenario involving force," he said.

Analysts said Yushchenko's move to send troops to Kiev was an attempt to pressure Yanukovych to agree on an early date for new parliamentary elections, rather than a sign he was preparing for violent confrontation.

"I think these maneuvers with security forces are meant to give the president a chance to maneuver at talks," said Vadim Karasyov, head of the Kiev-based Institute on Global Strategies.

Ukraine has suffered chronic political turmoil since Yushchenko came to office in 2005 after the Orange Revolution protests. The demonstrations broke out after Yanukovych was counted as winner of a fraud-plagued presidential ballot. The Supreme Court annulled that vote and Yushchenko won a rerun.

In the course of the race, Yushchenko was poisoned with dioxin, and the mystery of who might have done it, and why, has never been solved.